Terahertz ellipsometer system, and method of use

ABSTRACT

A terahertz ellipsometer, the basic preferred embodiment being a sequential system having a backward wave oscillator (BWO); a first rotatable polarizer that includes a wire grid (WGP 1 ); a rotating polarizer that includes a wire grid (RWGP); a stage (STG) for supporting a sample (S); a rotating retarder (RRET) comprising first (RP), second (RM 1 ), third (RM 2 ) and fourth (RM 3 ) elements; a second rotatable polarizer that includes a wire grid (WGP 2 ); and a Golay cell detector (DET).

CROSS-REFERENCE TO OTHER APPLICATIONS

This application is a CIP of Ser. No. 13/506,848 Filed May 21, 2012 andtherevia of Ser. No. 12/802,734 Filed Jun. 14, 2010, and therevia ofSer. No. 12/802,638 Filed Jun. 11, 2010, and therevia is a CIP of Ser.No. 12/456,791 Filed Jun. 23, 2009, and via the foregoing Claims Benefitof Provisional Application Ser. No. 61/208,735 Filed Feb. 27, 2009, andfurther Claims Benefit of Provisional Application Ser. No. 61/281,905Filed Nov. 22, 2009.

STATEMENT OF FINANCIAL SUPPORT

This invention which is subject in this application was developed inpart under support provided by a Grant from the Army under Phase I ARMYSTTR Contract No. W911NF-08-C-01121.

The portion of this invention concerning the “odd bounce image rotationsystem and method of use” in this application was developed in partunder support provided by a Grant from the National Science Foundationunder Phase II SBIR Contract No. 9901510.

The United States Government has certain rights in this invention.

TECHNICAL FIELD

The present invention relates to ellipsometer and polarimeter systems,and more particularity to an ellipsometer or polarimeter or the likesystem operating at THZ frequencies, and ideally comprising a backwardwave oscilator; a frequency multiplier; a first concave parabolicmirror; a reflecting means; a first rotatable wire grid polarizer; asecond concave parabolic mirror; a rotating wire grid polarizer; a stagefor supporting a sample; a rotating retarder comprising first, second,third and fourth elements, a third concave parabolic mirror; a secondrotatable wire grid polarizer; a fourth concave parabolic mirror; and agolay cell detector.

BACKGROUND

The practice of ellipsometry is well established as a non-destructiveapproach to determining characteristics of sample systems, and can bepracticed in real time. The topic is well described in a number ofpublications, one such publication being a review paper by Collins,titled “Automatic Rotating Element Ellipsometers: Calibration, Operationand Real-Time Applications”, Rev. Sci. Instrum., 61(8) (1990).

Before proceeding, as it is relevant to the present invention, it isnoted that ellipsometer systems generally comprise means for setting alinear or elliptical polarization state, (typically substantiallylinear).

Continuing, in general, modern practice of ellipsometry typicallyinvolves causing a spectroscopic beam of electromagnetic radiation, in aknown state of polarization, to interact with a sample system at atleast one angle of incidence with respect to a normal to a surfacethereof, in a plane of incidence. (Note, a plane of incidence containsboth a normal to a surface of an investigated sample system and thelocus of said beam of electromagnetic radiation). Changes in thepolarization state of said beam of electromagnetic radiation which occuras a result of said interaction with said sample system are indicativeof the structure and composition of said sample system. The practice ofellipsometry further involves proposing a mathematical model of theellipsometer system and the sample system investigated by use thereof,and experimental data is then obtained by application of theellipsometer system. This is typically followed by application of asquare error reducing mathematical regression to the end that parametersin the mathematical model which characterize the sample system areevaluated, such that the obtained experimental data, and valuescalculated by use of the mathematical model, are essentially the same.

A typical goal in ellipsometry is to obtain, for each wavelength in, andangle of incidence of said beam of electromagnetic radiation caused tointeract with a sample system, sample system characterizing PSI andDELTA values, (where PSI is related to a change in a ratio of magnitudesof orthogonal components r_(p)/r_(s) in said beam of electromagneticradiation, and wherein DELTA is related to a phase shift entered betweensaid orthogonal components r_(p) and r_(s)), caused by interaction withsaid sample system. The governing equation is:ρ=rp/rs=Tan(Ψ)exp(iΔ)

As alluded to, the practice of ellipsometry requires that a mathematicalmodel be derived and provided for a sample system and for theellipsometer system being applied. In that light it must be appreciatedthat an ellipsometer system which is applied to investigate a samplesystem is, generally, sequentially comprised of:

-   -   a. a Source of a beam electromagnetic radiation;    -   b. a Polarizer element;    -   c. optionally a compensator element;    -   d. (additional element(s));    -   e. a sample system;    -   f. (additional element(s));    -   g. optionally a compensator element;    -   h. an Analyzer element; and    -   i. a Spectroscopic Detector System.        Each of said components b.-i. must be accurately represented by        a mathematical model of the ellipsometer system along with a        vector which represents a beam of electromagnetic radiation        provided from said source of a beam electromagnetic radiation,        Identified in a. above)

Various conventional ellipsometer configurations provide that aPolarizer, Analyzer and/or Compensator(s) can be rotated during dataacquisition, and are describe variously as Rotating Polarizer (RPE),Rotating Analyzer (RAE) and Rotating Compensator (RCE) EllipsometerSystems. It is noted, that nulling ellipsometers also exist in whichelements therein are rotatable in use, rather than rotating. Generally,use of a nulling ellipsometer system involves imposing a substantiallylinear polarization state on a beam of electromagnetic radiation with alinear polarizer, causing the resulting polarized beam ofelectromagnetic radiation to interact with a sample system, and thenadjusting an analyzer to an azimuthal azimuthal angle which effectivelycancels out the beam of electromagnetic radiation which proceeds pastthe sample system. The azimuthal angle of the analyzer at which nullingoccurs provides insight to properties of the sample system.

Continuing, in use, data sets can be obtained with an ellipsometersystem configured with a sample system present, sequentially for caseswhere other sample systems are present, and where an ellipsometer systemis configured in a straight-through configuration wherein a beam ofelectromagnetic radiation is caused to pass straight through theellipsometer system without interacting with a sample system.Simultaneous mathematical regression utilizing multiple data sets canallow calibration of ellipsometers and evaluation of sample systemcharacterizing PSI and DELTA values over a range of wavelengths. Theobtaining of numerous data sets with an ellipsometer system configuredwith, for instance, a sequence of sample systems present and/or whereina sequential plurality of polarization states are imposed on anelectromagnetic beam caused to interact therewith, can allow systemcalibration of numerous ellipsometer system variables.

It is further noted that it was disclosed in a Co-Pending Parentapplication Ser. Nos. 12/802,734 and 12/456,791 and 12/802,638, that thepresent invention is a practical ellipsometer or polarimeter system forapplication in the range of frequencies between 300 GHz or below. Inthat light it is to be understood that prior art demonstrates that it isnot unknown to propose, or provide a system for, and practice ofellipsometry at Terahertz (THz) frequencies, however, a specificembodiment than makes such possible and which is suitable for generalapplication in universities and industry etc., has not been previouslydisclosed. To the Applicant's knowledge, there are no commerciallyavailable THz ellipsometers or polarimeters available in the marketplace.

While Synchrotrons have been used to provide THz frequency bandelectromagnetic radiation in ellipsometers, it is not remotely possibleto provide a Synchrotron at every location whereat it is desired topractice THz ellipsometry. The present invention provides combination ofmany elements, which results in a novel, practical system for generalapplication in the market place.

Before proceeding, it is of benefit to define some terminology. First, agenerally accepted range for what constitutes a Terahertz range offrequencies is from 3×10¹¹ (ie. 300 GHz), to 1.3×10¹² (ie. 1.3 Thz),Hertz. The Terahertz range is sandwiched between the microwave, (thehigh end of which has a wavelength of 1 millimeter), and thefar-infrared, (the long-wavelength edge of which is 100 micrometers),ranges of wavelengths/frequencies.

Next, it is noted that a number of sources of Terahertz (THz)electromagnetic radiation exit. For instance, a Smith-Purcell cell is adevice which directs an energetic beam of electrons very close to aruled surface of a diffraction grating. The effect on the trajectory ofthe beam is negligible, but a result is that Cherenkov radiation in theTerahertz frequency range can be created, where the phase velocity ofthe electromagnetic radiation is altered by the periodic grating.Another source of Terahertz radiation is a Free Electron Laser. In thissource a beam of electrons is accelerated to relativistic speed andcaused to pass through a periodic transverse magnetic field. The arrayof magnets is sometimes called an undulator or “wiggler” as it causesthe electrons to form a sinusoidal path. The acceleration of theelectrons causes release of photons, which is “synchrotron radiation”.Further, the electron motion is in phase with the field of said releasedelectromagnetic radiation, and therefore the fields add coherently.Instabilities in the electron beam resulting from interactions of theoscillations in the undulators lead to emission of electromagneticradiation, wherein electrons radiate independently. The wavelength ofthe emitted electromagnetic radiation from the electrons can be adjustedby adjusting the energy of the electron beam and/or magnetic fieldstrength of the undulators, to be in the Terahertz range. Anothersource, (and preferred in the present invention), of Terahertzfrequencies is a Backward Wave Oscillator (BWO), which is a vacuum tubesystem comprising an electron gun that generates an electron beam andcauses it to interact with an electromagnetic wave traveling in adirection opposite to that of ejected electrons such that THz frequencyoscillations are sustained by interaction between the propagatingtraveling wave backwards against the electron beam.

It is also disclosed that numerous detectors exist for monitoringTerahertz range electromagnetic radiation. One example is a Golay cellwhich operates by converting a temperature change resulting fromelectromagnetic radiation impinging onto material, into a measurablesignal. Generally, when electromagnetic radiation is caused to impingeon a blackened material it heats a gas, (eg. Xenon) in an first chamberof an enclosure, and that causes a distortable reflecting diaphram/filmadjacent to said first chamber to change shape. In a second chamber,separated from the first by said diaphram/film an electromagnetic beamis caused to reflect from the film and into a photocell, which in turnconverts the received electromagnetic radiation into an electricalsignal. A Bolometer is another detector of monitoring Terahertz rangeelectromagnetic radiation, but operates by using the effect of achanging electric resistance caused by electromagnetic radiationimpinging onto a blackened metal.

It is also noted that there are Solid State sources and detectors ofTerahertz frequency electromagnetic radiation. For instance, anidentified reference by Nagashima et al. discloses that THz pulses canbe generated by a bow-tie photoconductive radiation antenna excited by amode-locked Ti-sapphire laser with 80 Fs time width pulses, and adetection antenna can be formed from a dipole-type photoconductiveantenna with a 5 micron gap fabricated on thin film LT-GaAs. Further, itis known that a company named AB Millimeter in Paris France, supplies asystem that covers the entire range from 8 GHz to 1000 GHz with solidstate source and detector devices.

Before disclosing known references, it is noted that computer searchingat the PTO Website for Patents and Published Applications containing thewords:

-   -   (ellipsometer & bolometer); and    -   (ellipsometer & Golay cell);        produced only one hit, that being Published Application        US2005/0175507 by Tsukruk. Said 507 reference does contain the        words ellipsometry and Golay, but does not describe an        ellipsometer system comprising said elements.

Further, a PTO Website Search for Patents and Published Applicationscontaining the words:

-   -   (ellipsometer & backward wave oscillator);    -   (ellipsometer & Smith-Purcell); and    -   (ellipsometer & free electron laser);        produced only U.S. Pat. No. 5,317,618 to Nakahara et al., which        contains the words ellipsometer & free electron laser, but does        not describe a combination of said elements.

A Patent to Wang et al., U.S. Pat. No. 5,914,492 is of interest as itdescribes free electron lasers used in combination with a Golay cell andSmith-Purcell detectors. However, it does not describe application inellipsometry or polarimetry.

A Published Application, US2006/0050269 by Brownell describes use of afree electron laser and a Smith-Purcell detector, but not in the contextof ellipsometry or polarimetry.

An article titled “Gain of a Smith-Purcell Free Electron Laser”, Andrewset al., Phy. Rev., Vol 7, 070701 (2004), describes use of Smith-PurcellFree Electron Laser.

U.S. Pat. No. 2,985,790 to Kompfner is disclosed as it describes aBackward Wave Oscillator.

U.S. Pat. No. 2,880,355 to Epsztein is disclosed as it describes aBackward Wave Oscillator.

Known References which describe Ellipsometers which operate in the THzfrequency range are:

-   -   “Terahertz Generalized Meuller-matrix Ellipsometery”, Hofmann et        al., Proc. of SPIE, Vol. 6120, pp. 61200D1-61200D10, (2005),        describes applying Thz electromagnetic radiation in generalized        ellipsometry wherein the source of the Thz electromagnetic        radiation is a synchrotron located at BESSY, in Germany.    -   “Terahertz magneto-optic generalized ellipsometry using        synchrotron and blackbody radiation”, Hofmann et al., American        Inst. of Physics, 77, 063902-1 through 063902-12, (2006),        describes applying Thz electromagnetic radiation in generalized        ellipsometry wherein the source of the Thz electromagnetic        radiation is a synchrotron and a conventional blackbody. The use        of an FTIR source and bolometer is also mentioned.    -   “Label-free Amplified Bioaffinity Detection Using Terahertz Wave        Technology”, Menikh et al., Biosensors and Bioelectronics 20,        658-662 (2004), describes use of an unbiased GaAs crystal THz        source of electromagnetic radiation and a ZnTe crystal detector.    -   Spectroscopy by Pulsed Terahertz Radiation”, Hango et al., Meas.        Sci. and Technol., 13 (2002), pp 1727-1738, describes applying        30 GHz-10 THz and describes use of Fourier Transform        Spectrometers (FTS) in the Far Infrared (FIR) frequency range        with the caution that such an approach is not easily applied        below 1 THz. Said reference also describes application of        Backward Wave Oscillators (BWO) plus frequency multipliers, with        the caution that to cover the range of 30 GHz to 3 THz typically        requires many BWO's and frequency multipliers to cover said        frequency range. This article favors use of a Femto-sec laser        (eg. a mode-locked Ti:sapphire laser or Er-doped fiber laser in        combination with a photoconductive antenna made on        low-temperature grown GaAs).    -   “Measurement of Complex Optical Constants of a Highly Doped Si        Wafer Using Terahertz Ellipsometry”, Nagashima et al., Applied        Phys. Lett. Vol. 79, No. 24 (10 Dec. 2001). This article        describes use of a mode-locked Ti:sapphire laser with a bow-tie        antenna and GaAs detector antenna).    -   Published Patent Application No. US2004/0027571 by Luttman        mentions using a THz light Source in an ellipsometer system.    -   “Development of Terahertz Ellipsometry and its Application to        Evaluation of Semiconductors”, Nagashima et al., Tech. Meeting        on Light Application and Visual Science, IEEE (2002) proposes a        Terahertz ellipsometer.    -   “Terahertz Imaging System Based on a Backward-Wave Oscillator,        Dobroiu et al., Applied Optics, Vol. 43, No 30, (20 Oct. 2004)        describes use of a Terahertz source to provide electromagnetic        radiation.

A Patent to Herzinger et al. U.S. Pat. No. 6,795,184, describes an“Odd-Bounce” system for rotating a polarization state in anelectromagnetic beam. Patents disclosed in the Application leading toU.S. Pat. No. 6,795,184 are:

-   -   Patent to Herzinger, U.S. Pat. No. 6,137,618 is disclosed as it        describes a Single Brewster Angle Polarizer in the context of        multiple reflecting means, and discloses prior art dual Brewster        Angle Single Reflective Means Polarizer Systems.    -   Patent, to Herzinger et al., U.S. Pat. No. 6,084,675 describes        an adjustable beam alignment compensator/retarder with        application to spectroscopic ellipsometry.    -   U.S. Pat. No. 6,118,537 to Johs et al. describes a multiple        Berek plate optical retarder system.    -   U.S. Pat. No. 6,141,102 to Johs et al. describes a single        triangular shaped optical retarder element.    -   U.S. Pat. No. 5,946,098 to Johs et al., describes dual tipped        wire grid polarizers in combination with various        compensator/retarder systems.    -   U.S. Pat. No. 6,100,981 to Johs et al., describes a dual        horizontally oriented triangular shaped optical retarder.    -   U.S. Pat. No. 6,084,674 to Johs et al., describes a        parallelogram shaped optical retarder element.    -   U.S. Pat. No. 5,963,325 to Johs et al., describes a dual        vertically oriented triangular shaped optical retarder element.    -   U.S. Pat. No. 7,450,231 and U.S. Pat. No. 7,460,230 to Johs et        al. are disclosed as they describe deviation angle self        compensating compensator systems.    -   A Patent to Johs et al., U.S. Pat. No. 5,872,630 is disclosed as        it describes an ellipsometer system in which an analyzer and        polarizer are maintained in a fixed in position during data        acquisition, while a compensator is caused to continuously        rotate.    -   A Patent to Thompson et al. U.S. Pat. No. 5,706,212 is also        disclosed as it teaches a mathematical regression based double        Fourier series ellipsometer calibration procedure for        application, primarily, in calibrating ellipsometers system        utilized in infrared wavelength range. Bi-refringent,        transmissive window-like compensators are described as present        in the system thereof, and discussion of correlation of        retardations entered by sequentially adjacent elements which do        not rotate with respect to one another during data acquisition        is described therein.    -   Further Patents disclosed in the 184 Patent are:        -   U.S. Pat. No. 5,757,494; and            -   U.S. Pat. No. 5,956,145;    -   to Green et al., in which are taught a method for extending the        range of Rotating Analyzer/Polarizer ellipsometer systems to        allow measurement of DELTA'S near zero (0.0) and        one-hundred-eighty (180) degrees, and the extension of modulator        element ellipsometers to PSI'S of forty-five (45) degrees. Said        Patents describes the presence of a variable, transmissive,        bi-refringent component which is added, and the application        thereof during data acquisition to enable the identified        capability.    -   A Patent to He et al., U.S. Pat. No. 5,963,327 is disclosed as        it describes an ellipsometer system which enables providing a        polarized beam of electromagnetic radiation at an oblique        angle-of-incidence to a sample system in a small spot area.    -   Patents of general interest disclosed in the 184 Patent include:        -   Patent to Woollam et al, U.S. Pat. No. 5,373,359, (describes            a beam chopper);        -   Patent to Johs et al. U.S. Pat. No. 5,666,201;        -   Patent to Green et al., U.S. Pat. No. 5,521,706; and        -   Patent to Johs et al., U.S. Pat. No. 5,504,582;            and are disclosed as they pertain to ellipsometer systems.    -   A Patent to Coates et al., U.S. Pat. No. 4,826,321 is disclosed        as it describes applying a reflected monochromatic beam of plane        polarized electromagnetic radiation at a Brewster angle of        incidence to a sample substrate to determine the thickness of a        thin film thereupon. This Patent also describes calibration        utilizing two sample substrates, which have different depths of        surface coating.    -   Other Patents which describe use of reflected electromagnetic        radiation to investigate sample systems are:        -   U.S. Pat. No. RE 34,783,            -   U.S. Pat. No. 4,373,817,            -   U.S. Pat. No. 5,045,704    -   to Coates; and        -   U.S. Pat. No. 5,452,091    -   to Johnson.    -   A Patent to Bjork et al., U.S. Pat. No. 4,647,207 is disclosed        as it describes an ellipsometer system which has provision for        sequentially, individually positioning a plurality of reflective        polarization state modifiers in a beam of electromagnetic        radiation. U.S. Pat. Nos. 4,210,401; 4,332,476 and 4,355,903 are        also identified as being cited in the 207 Patent. It is noted        that systems as disclosed in these Patents, (particularly in the        476 Patent), which utilize reflection from an element to modify        a polarization state can, if such an element is an essential        duplicate of an investigated sample and is rotated ninety        degrees therefrom, the effect of the polarization state        modifying element on the electromagnetic beam effect is        extinguished by the sample.    -   A Patent to Mansuripur et al., U.S. Pat. No. 4,838,695 is        disclosed as it describes an apparatus for measuring        reflectivity.    -   Patents to Rosencwaig et al., U.S. Pat. Nos. 4,750,822 and        5,596,406 are also identified as they describe systems which        impinge electromagnetic beams onto sample systems at oblique        angles of incidence. The 406 Patent provides for use of multiple        wavelengths and multiple angles of incidence. For similar        reasons U.S. Pat. No. 5,042,951 to Gold et al. is also        disclosed.    -   In addition to the identified Patents, certain Scientific papers        were also disclosed in the 184 Patent are:    -   A paper by Johs, titled “Regression Calibration Method for        Rotating Element Ellipsometers”, Thin Solid Films, 234 (1993) is        also disclosed as it describes a mathematical regression based        approach to calibrating ellipsometer systems.

An additional relevant Patent is U.S. Pat. No. 6,268,917 to Johs. ThisPatent describes a combined polychromatic electromagnetic radiation beamsource comprising beam combiners.

It is also disclosed that the J. A. Woollman Co., Inc. has marketed anIR range Ellipsometer, called the IR-VASE (Reg. TM), for many years.Said instrument provides capability from 10 THz to 150 THz and is aVariable Angle, Rotating Compensator system utilizing a Bomen FTIRSpectrometer. Further, it comprises an FTIR Source, and an Odd-Bounceimage rotating system for rotating a polarization state imposed by awire-grid polarizer. It is noted that as marketed, this system has neverprovided the capability to reach down to 1 THz, which capability wasachieved via research in developing the present invention.

Additional references which describe ellipsometry practiced in the THzrange are:

-   -   “THz Ellipsometry in Theory and Experiment”, Dietz et al. 33rd        International Conference on Infrared and Millimeter Waves and        16th International Conference on Terahertz Electronics,        IRMMW-THz (2008) describes an experimental ellipsometer for use        in the THz frequency range;    -   “Study Terahertz Ellipsometry Setups for Measuring Metals and        Dielectrics Using Free Electron Laser Light Source”, Rudych,        31st International Conference on Infrared and Millimeter Waves        and 14th International Conference on Terahertz Electronics,        IRMMW-THz (2006) describes use of a free electron laser to        provide THz frequencies;    -   “Spectral THz Ellipsometer for the Unambiguous Determination of        all Stokess Parameters”, Holldack et al., 30th International        Conference on Infrared and Millimeter Waves and 13th        International Conference on Terahertz Electronics,        IRMMW-THz (2006) describes a concept for determining all Stokes        Parameters;    -   “Terahertz Magneto-Optic Generalized Ellipsometry Using        Synchrotron and Blackbody Radiation”, Esquinazi et al., Sci.        Instrum., Vol. 7, No. 6 (2006) describes use of synchrotron        generated electromagnetic radiation in magneto-optic generalized        ellipsometry;    -   “Terahertz Generalized Mueller-Matrix Ellisometry”, Esquinazi et        al. Proc. Int. Soc. Opt. Eng., Vol. 6120, (2006) describes        synchrotron generated electromagnetic radiation in generalized        Mueller Matrix ellipsometry    -   “THz Time-Domain Magneto-Optic Ellipsometry in Reflection        Geometry”, Kuwata-Gonokami et al., Trends Opt. Photonics Series,        Vol. 97, (2004) describes determining a dielectric tensor using        THz frequencies in magneto-optic optical measurements;    -   “Terahertz Polarimetry”, Gallot et al., Conf. Lasers        Electro-Optics, CLEO, Vol. 3 (2005) describes determining the        polarization state of a THz wave over a wide range of        frequencies;    -   “Evaluation of Complex Optical Constants of Semiconductor Wafers        using Terahertz Ellipsometry”, Hangyo et al., Trends Opt.        Photonics Series, Vol. 88, (2003) describes combined terahertz        ellipsometry with time domain spectroscopy.

Additional references which describe sources of Terahertz frequencyrange electromagnetism are:

-   -   “Improved Performance of Hybrid Electronic Terahertz        Generators”, Hurlbut et al., 33rd International Conference on        Infrared and Millimeter Waves and Terahertz Waves, IRMMW-THz        (2008), describes combining BWO's with frequency multipliers;    -   “Terahertz Wave Generation in Orientation-Patterned GaAs Using        Resonantly Enhanced Schemes”, Vodopyanov et al., SPIE-Intl. Soc.        for Opt. Eng. USA, Vol. 6455, (2007), describes application of        Zincblende semiconductors (GaAs, GaP) to produce THz        frequencies;    -   “Terahertz BWO Spectroscopy of Conductors and Superconductors”,        Gorshunov et al., Quantum Electronics, Vol. 37, No. 10 (October        2007), describes methods for directly measuring dielectric        response spectra of dielectrics, conductors and superconductors        using BWO generated spectrometers;    -   “Portable THz Spectrometers”, Kozlov et al., 31st International        Conference on Infrared and Millimeter Waves and 14th        International Conference on Terahertz Electronics, IRMMW-THz        (2007), describes a portable THz spectrometer which operates in        the frequency range of 0.1-1 THz;    -   “Terahertz Time-Domain Spectrsocopy”, Nishizawa et al.,        Terahertz Optoelectronics, Topics Appl. Phys. 97, 203-271        (2005).    -   U.S. Pat. No. 7,339,718 to Vodopanov et al., Issued Apr. 3, 2008        describes a method for generating THz radiation comprising        illuminating a semiconductor with an optical pulse train.    -   U.S. Pat. No. 6,819,423 to Stehle et al., Issued Nov. 16, 2004        and U.S. Pat. No. 5,317,618 Issued Jan. 25, 2005 are also        identified as they mention application of THz frequencies in an        ellipsometer system.

It is noted that the Search Report for a co-pending PCT Application,PCT/US09/05346, was recently received. It identified the followingreferences: U.S. Pat. Nos. 6,795,184; 7,274,450 and 6,798,511; andPublished Applications Nos. US2004/0228371; US2007/0252992;US2006/0289761; US2007/0278407; US2007/0097373. Also identified were: aPh.D. dissertation by Duerr, Erik Kurt, titled “DistributedPhotomixers”, Mass. Inst. Tech., September 2002; and article titled“Hole Diffusion Profile in a P−P+ Slicon Homoiunction Determined byTerahertz and Midinfrared Spectroscopic Ellipsometry”, Hofmann et al.,App. Phys. Lett., 95 032102 (2009).

The identified references, application Ser. No. 12/456,791, ProvisionalApplication Ser. No. 61/208,735 and Ser. No. 61/281,905, are allincorporated by reference into this Specification.

Further, in view of Examine Action leading to Allowance of Parentapplication Ser. No. 13/506,848 it is noted that the PublishedApplication by Nagashima et al. No. 2003/0016358 specifically calls forapplication of a LASER, (ie. a Single Wavelength), Source within a rangeof 0.2 to 0.8 THZ. In view thereof, Claims herein are presented hereinwhich specifically avoid the Nagashima et al. No. 2003/0016358 limitedTHZ range and require a non-laser Source in the Present Invention.

In addition, it is noted that the cited Nagashima et al. No.2003/0016358 reference describes a time-domain polarization analyzingapparatus. It is completely different from an Ellipsometer/polarimeter.It is also emphasised that the present invention provides a continuouswave Source, whereas the 358 reference applies a Laser Source. Further,the 358 reference splits the pulses generated and directs them alongdifferent pathways, then recombine them to provide interference. It thendescribes calculating sample characteristics much differently than doesthe present invention. Further, although not particularly important, itwas noted that the element (50) in the 358 reference is a computer, notthe detector, which is element (7). And, it was noted to me that thepresent invention Polarizer does not change direction of a beam, itsimply sets a polarization state therein. If required to furtherdistinguish the present invention, the relevant Polarizers in thepresent invention could be designated as not changing the direction ofthe beam as shown in FIG. 8 a of the Original Specification.

Finally, nothing in the 358 reference remotely suggests using other thana Laser Source, or doing away with the use of Pulsing or Interference,as the invention therein would simply not work if any of those thingswere done. Therefore, nothing in the 385 reference remotely leads one tothe Present Invention. Simply because some remotely similar elements arepresent in the 385 system and the Present Invention System, (which aredifferently applied to arrive at different results in different ways),does not remotely obviate the Present Invention. There are noinstructions in any cited prior art that would guide one skilled in theart to begin with the 385 invention and arrive at the Present Invention!

Even in view of relevant prior art, there remains need for anellipsometer or polarimeter system for application in the Terahertzregion, preferably in combination with a convenient approach toproviding linearly polarized beams of electromagnetic radiation in whichthe azimuthal angle of the linear polarization can be controlled.

DISCLOSURE OF THE INVENTION

In very broad terms, the present invention is a terahertz ellipsometeror polarimeter system that, in a basic form, sequentially comprises:

-   -   a source (BWO) of terahertz electromagnetic radiation;    -   a rotatable polarizer (WGP1);    -   a stage (STG) for supporting a sample (S);    -   a second rotatable polarizer (WGP2); and    -   a detector (DET) of terahertz electromagnetic radiation.        Said terahertz ellipsometer or polarimeter system further        comprises a first rotating element (RE1) and second rotating        element (RE2) between said source and said detector of        electromagnetic radiation, which can both be on the source or        detector side of the stage (STG), but preferably has on thereof        on each side.

The present invention is more specifically a terahertz ellipsometer orpolarimeter system that sequentially comprises:

-   -   a backward wave oscillator (BWO);    -   a rotatable polarizer comprising a wire grid (WGP1);    -   a stage (STG) for supporting a sample (S);    -   a second rotatable polarizer comprising a wire grid (WGP2); and    -   a Golay cell detector (DET).        Said terahertz ellipsometer or polarimeter system further        comprises a first rotating element (RE1) and second rotating        element (RE2) between said backward wave oscillator (BWO) and        said a Golay cell detector (DET) which can both be on the        backward wave oscillator (BWO) or Golay cell detector (DET) side        of the stage (STG), but preferably has on thereof on each side.        In use said backward wave oscillator (BWO) directs a beam (BI)        of terahertz frequency electromagnetic radiation of a        fundamental frequency to pass through said first rotatable        polarizer comprising a wire grid (WGP1), then reflect from a        sample (S) placed on said stage (STG) for supporting a sample,        then pass through said second rotatable polarizer comprising a        wire grid (WGP2), and, as output beam (BO) enter said Golay cell        detector (DET) as output beam (BO), said beam also passing        through the first (RE1) and second (RE2) rotating elements.

As alluded to, a preferred embodiment provides that said first rotatingelement (RE1) and second rotating element (RE2) are on the (BWO) and(DET) sides of said stage (STG) and sample, receptively, such that, inuse, said backward wave oscillator (BWO) directs a beam (BI) ofterahertz frequency electromagnetic radiation of a fundamental frequencyto pass through said first rotatable polarizer comprising a wire grid(WGP1), then through said first rotating element (RE1), then reflectfrom a sample (S) placed on said stage (STG) for supporting a sample,then pass through said second rotating element (RE2), then pass throughsaid second rotatable polarizer comprising a wire grid (WGP2), and, asoutput beam (BO) enter said Golay cell detector (DET) as output beam(BO).

Said terahertz ellipsometer or polarimeter system can provide that thefirst (RE1) and second (RE2) rotating elements are each selected fromthe group consisting of:

-   -   one thereof is a rotating polarizer comprising a wire grid        (RWGP); and    -   the other thereof is a rotating retarder (RRET) comprising, in        any functional order, first (RP), second (RM1), third (RM2) and        fourth (RM3) reflective elements from each of which, in use, an        electromagnetic beam reflects once, said first reflective        element (RP) being prism (RP) which receives a beam through a        first side thereof and exits a reflected beam through a third        side thereof, said reflection being from a second side thereof        oriented at prism forming angles to said first and third sides;        said elements (RP) (RM1) (RM2) (RM3) being oriented with respect        to one another such that the locus of the beam reflecting from        the second side of said prism approaches said second reflective        side thereof at an angle equal to or greater than that required        to achieve total internal reflection within said prism (RP), and        such that the locus of beam reflected from the fourth element in        the sequence of elements is substantially colinear and without        deviation or displacement from the locus of the beam received by        the first element in said sequence of elements.        (Note, the preferred embodiment provides the first rotating        element (RE1) be a rotating polarizer comprising a wire grid        (RWGP) and the second rotating element (RE2) be a rotating        retarder (RRET) comprising, in any functional order, said first        (RP), second (RM1), third (RM2) and fourth (RM3) reflective        elements, with the preferred configuration of (RRET) being that        the said prism (RP) be placed so as to first encounter an input        beam).

Said basic terahertz ellipsometer or polarimeter can furthersequentially comprise:

-   -   a frequency multiplier (FM) following said backward wave        oscillator (BWO);    -   a first concave parabolic mirror (PM1); and    -   a reflecting means (M1);        prior to said rotatable polarizer comprising a wire grid (WGP1).        Further, after said polarizer comprising a wire grid (WGP1) said        terahertz ellipsometer or polarimeter can further comprise:    -   a second concave parabolic mirror (PM2);        prior to said a first rotating element (RE1).        And, there can further sequentially be, after said second        rotating element (RE2), a third concave parabolic mirror (PM3).        Also, further sequentially after said second rotatable polarizer        comprising a wire grid (WGP2) there can be:    -   a fourth concave parabolic mirror (PM4) prior to said Golay cell        detector (DET).        In use, with the foregoing additional elements in place, said        backward wave oscillator (BWO) directs a beam (BI) of terahertz        frequency electromagnetic radiation of a fundamental frequency        to said frequency multiplier (FM), from which frequency        multiplier (FM) a beam comprising a desired frequency is caused        to be reflected from said first concave parabolic mirror (PM1)        as a substantially collimated beam, said substantially        collimated beam then being directed to reflect from said        reflecting means (M1) and pass through said first rotatable        polarizer comprising a wire grid (WGP1) and reflect from said        second concave (PM2) parabolic mirror through said first        rotating element (RE1), then reflect from a sample (S) placed on        said stage (STG) for supporting a sample, then pass through said        second rotating element (RE2), reflect from said third parabolic        mirror (PM3), pass through said second rotatable polarizer        comprising a wire grid (WGP2), then reflect from said fourth        concave parabolic mirror (PM4) and enter said Golay cell        detector (DET) as output beam (BO).

More simply, said basic terahertz ellipsometer or polarimeter canfurther comprise, between said backward wave oscillator (BWO) and saidGolay cell detector (DET) at least one selection from the groupconsisting of:

-   -   at least one concave parabolic mirror (PM1) (PM2) (PM3) (PM4);        and    -   at least one reflecting means (M1).

More simply, said basic terahertz ellipsometer or polarimeter canfurther comprise a frequency multiplier (FM) following said backwardwave oscillator (BWO).

Said basic terahertz ellipsometer or polarimeter can further comprise achopper (CHP) between said backward wave oscillator (BWO) and said Golaycell detector (DET).

Said basic terahertz ellipsometer or polarimeter system can furthercomprise means for rotating, as a unit, said:

stage (STG) for supporting a sample (S); second rotating element, thirdconcave parabolic mirror (PM3) if present; second rotatable polarizercomprising a wire grid (WGP2); fourth concave parabolic mirror (PM4) ifpresent; and Golay cell detector (DET);

and/or as a unit said:

stage (STG) for supporting a sample (S); first rotating element; secondconcave parabolic mirror (PM2) if present; rotatable polarizercomprising a wire grid (WGP1); reflecting means (M1) if present; firstconcave parabolic mirror (PM1) if present; frequency multiplier (FM) ifpresent; and backward wave oscillator (BWO);about a vertical axis centered at a midpoint of said stage (STG) forsupporting a sample (S). This enables control of the angle of incidence(0) at which said beam of terahertz frequency electromagnetic radiationapproaches said sample (S) from said rotating polarizer comprising awire grid (RWGP), and the angle of reflection (0) of said beam from saidsample (S) placed on said stage (STG) for supporting a sample.

Said basic terahertz ellipsometer or polarimeter system can provide thatthe stage (STG) for supporting a sample (S) is oriented to support asample in a substantially vertical plane, or in a substantiallyhorizontal plane.

Where the stage is oriented substantially horizontally, a system forenabling this can involve receiving a beam exiting said first rotatingelement (RE1) and directing it thereto via left and right verticalsequences, each of first (FLS/FRS), second (SLS/SRS) and third (TLS/TRS)elements, such that the terahertz frequency electromagnetic beam exitingsaid first rotating element reflects from the first left side element(FLS) to the second left side element (SLS), then to the third rightside element (TRS), from which it is directed to reflect from a sample(S) placed on the stage (STG) in a substantially horizontal plane towardthe third left side element (TLS), which reflects said beam to thesecond right side element (SRS) toward said first right side element(FRS), from which said beam is directed into said second rotatingelement (RE2).

Said terahertz ellipsometer or polarimeter system can involve a rotatingpolarizer that comprises a wire grid selected from the group consistingof:

-   -   a dual polarizing component system comprising non-Brewster Angle        (NBR) and Brewster (BR) Angle components, wherein a beam of        electromagnetic radiation that passes through said (NBR)        reflects from additional reflective means (M1) and (M2), then        from (BR), and continues as a polarized beam); and    -   a dual tipped wire grid polarizer system comprising first (WG1)        and second (WG2) wire grid polarizers which have fast axes of        polarization oriented with their fast axes parallel to one        another, each thereof having first and second essentially        parallel surfaces, such that essentially parallel sides of (WG1)        are tipped with respect to the essentially parallel sides of        (WG2), wherein a beam entering one of said first and second wire        grid polarizers exits the second thereof in a polarized state,        with unwanted reflections (R1) and (R2) being diverted away.

Said terahertz ellipsometer or polarimeter can further comprise at leastone aperture (A) between said backward wave oscillator (BWO) and saidGolay cell detector (DET).

It is also noted that said terahertz ellipsometer or polarimeter systemcan provide that the first (RE1) and second (RE2) rotating elements arerotated at relative speeds with respect to one another that form a ratioin the range of 1 to 10 or in the range of 10 to 1.

A method of determining physical and optical properties of samples usinga terahertz frequency electromagnetic radiation utilizing a preferredembodiment of the present invention, comprises the steps of:

-   -   a) providing a terahertz ellipsometer or polarimeter system        sequentially system comprising:    -   a backward wave oscillator (BWO);    -   a rotatable polarizer comprising a wire grid (WGP1);    -   a rotating polarizer comprising a wire grid (RWGP);    -   a stage (STG) for supporting a sample (S);    -   a rotating retarder (RRET) comprising, in any functional order,        first (RP), second (RM1), third (RM2) and fourth (RM3)        reflective elements from each of which, in use, an        electromagnetic beam reflects once, said first reflective        element (RP) being prism (RP) which receives a beam through a        first side thereof and exits a reflected beam through a third        side thereof, said reflection being from a second side thereof        oriented at prism forming angles to said first and third sides;        said elements (RP) (RM1) (RM2) (RM3) being oriented with respect        to one another such that the locus of the beam reflecting from        the second side of said prism approaches said second reflective        side thereof at an angle equal to or greater than that required        to achieve total internal reflection within said prism (RP), and        such that the locus of beam reflected from the fourth element in        the sequence of elements is substantially colinear and without        deviation or displacement from the locus of the beam received by        the first element in said sequence of elements.    -   a second rotatable polarizer comprising a wire grid (WGP2);    -   a Golay cell detector (DET);        such that in use said backward wave oscillator (BWO) directs a        beam (BI) of terahertz frequency electromagnetic radiation of a        fundamental frequency to pass through said first rotatable        polarizer comprising a wire grid (WGP1), then through said        rotating polarizer comprising a wire grid (RWGP), then reflect        from a sample (S) placed on said stage (STG) for supporting a        sample, then pass through said rotating retarder (RRET), then        pass through said second rotatable wire grid polarizer (WGP2),        enter said Golay cell detector (DET) as output beam (BO).        Said method continues with:    -   b) placing a sample (S) on said stage (STG) for supporting        samples;    -   c) causing said backward wave oscillator (BWO) to direct a beam        (BI) of terahertz frequency electromagnetic radiation of a        fundamental frequency to pass through said first rotatable wire        grid polarizer (WGP1) and then through said rotating polarizer        comprising a wire grid (RWGP), then reflect from a sample (S)        placed on said stage (STG) for supporting a sample, then pass        through said rotating retarder (RRET), then pass through said        second rotatable polarizer comprising a wire grid (WGP2), and        enter said Golay cell detector (DET) as output beam (BO);    -   d) obtaining sample describing data from said Golay cell        detector (DET).

Said method can involve that the step of providing a terahertzellipsometer or polarimeter system further comprises providing:

-   -   a frequency multiplier (FM) following said backward wave        oscillator (BWO);    -   a first concave parabolic mirror (PM1); and    -   a reflecting means (M1);        prior to said rotatable polarizer comprising a wire grid (WGP1);        and which further sequentially comprises after said rotatable        polarizer comprising a wire grid (WGP1);    -   a second concave parabolic mirror (PM2);        prior to said a rotating polarizer comprising a wire grid        (RWGP);        there also further sequentially being, after said rotating        retarder (RRET), a third concave parabolic mirror (PM3);        and there also further sequentially being, after said second        rotatable polarizer comprising a wire grid (WGP2);    -   a fourth concave parabolic mirror (PM4) prior to said Golay cell        detector (DET);        such that in use said backward wave oscillator (BWO) directs a        beam (BI) of terahertz frequency electromagnetic radiation of a        fundamental frequency to said frequency multiplier (FM), from        which frequency multiplier (FM) a beam comprising a desired        frequency is caused to be reflected from said first concave        parabolic mirror (PM1) as a substantially collimated beam, said        substantially collimated beam then being directed to reflect        from said reflecting means (M1) and pass through said first        rotatable polarizer comprising a wire grid (WGP1) and reflect        from said second concave (PM2) parabolic mirror through said        rotating polarizer comprising a wire grid (RWGP), then reflect        from a sample (S) placed on said stage (STG) for supporting a        sample, then pass through said rotating retarder (RRET), reflect        from said third parabolic mirror (PM3), pass through said second        rotatable polarizer comprising a wire grid (WGP2), then reflect        from said fourth concave parabolic mirror (PM4) and enter said        Golay cell detector (DET) as output beam (BO).

Said method can involve the sample (S) being oriented in a substantiallyvertical plane while data is obtained from said Golay cell detector(DET).

Said method can involve the sample (S) being oriented in a substantiallyhorizontal plane, and a preferred approach by which this can beaccomplished comprises application of a system comprising left and rightvertical sequences of first (FLS/FRS), second (SLS/SRS) and third(TLS/TRS) elements, such that the terahertz frequency electromagneticbeam exiting said rotating polarizer comprising a wire grid (RWGP)reflects from the first left side element (FLS) to the second left sideelement (SLS), then to the third right side (TRS) element, from which itis directed to reflect from a sample (S) placed on the stage (STG) in asubstantially horizontal plane toward the third left side (TLS) element,which reflects said beam to the second right side element (SRS) towardsaid first right side element (FRS), from which said beam is directedinto said second rotating retarder (RE2).

Said method can further comprise providing means for rotating, as aunit, said:

stage (STG) for supporting a sample (S); rotating retarder (RRET), thirdconcave parabolic mirror (PM3) if present; second rotatable polarizercomprising a wire grid (WGP2); fourth concave parabolic mirror (PM4) ifpresent; and Golay cell detector (DET);

and/or as a unit said:

stage (STG) for supporting a sample (S); rotating wire grid polarizer(RWGP); second concave parabolic mirror (PM2) if present; rotatablepolarizer comprising a wire grid (WGP1); reflecting means (M1) ifpresent; first concave parabolic mirror (PM1) if present; frequencymultiplier (FM) if present; and backward wave oscillator (BWO);about a vertical axis centered at a midpoint of said stage (STG) forsupporting a sample (S) such that the angle of incidence (0) at whichsaid beam of terahertz frequency electromagnetic radiation approachingfrom said rotating polarizer comprising a wire grid (RWGP), and theangle of reflection (0) of said beam from said sample (S) placed on saidstage (STG) for supporting a sample, can be adjusted; andprior to step d causing rotation of the unit about said verticalmidpoint axis of said stage.

Said method can further involve providing a chopper (CHP), said chopper(CHP) being a rotating wheel with a plurality of openings thereinthrough which the terahertz electromagnetic radiation beam can pass,said chopper (CHP) being placed the locus of the terahertzelectromagnetic radiation beam at some point between said backward waveoscillator and said Golay cell detector, and during the step d obtainingof data, causing said chopper to chop said terahertz frequency beam.

Said method can involve rotating the rotating polarizer comprising awire grid (RWGP) and the rotating retarder (RRET) comprising first (RP),second (RM1), third (RM2) and fourth (RM3) elements, at relative speedswith respect to one another that form a ratio in the range of 1 to 10 orin the range of 10 to 1 during the step d obtaining of data.

Finally, said method can further comprise performing at least oneselection from the group consisting of:

-   -   storing at least some data provided by said Golay cell detector        in machine readable media;    -   analyzing at least some of the data provided by said Golay cell        detector and storing at least some of the results of said        analysis in machine readable media;    -   displaying at least some data provided by said Golay cell        detector by electronic and/or non-electronic means;    -   analyzing at least some of the data provided by said Golay cell        detector and displaying at least some of the results of said        analysis by electronic and/or non-electronic means;    -   causing at least some data provided by said Golay cell detector        to produce a signal which is applied to provide a concrete and        tangible result;    -   analyzing at least some of the data provided by said Golay cell        detector and causing at least some thereof to produce a signal        which is applied to provide a concrete and tangible result.

Previously Disclosed Material Provided for Support

As additional support the following, which was previously disclosed indisclosed in a Co-Pending Parent application Ser. Nos. 12/802,734 and12/456,791, is provided to further disclose that the present inventioncomprises, or can further comprise a practical ellipsometer orpolarimeter system for application in the range of frequencies between300 GHz or below and proceeding well into and preferably through theInfrared frequency range. The prior art demonstrates that it is notunknown to propose, or provide a system for, and practice ofellipsometry at Terahertz (THz) frequencies, however, a specificembodiment than makes such possible and which is suitable for generalapplication in universities and industry etc., has not been previouslydisclosed. To the Applicant's knowledge, there are no commerciallyavailable THz ellipsometers or polarimeters available in the marketplace. This is even more so the case where the ellipsometer orpolarimeter also provides Infrared (IR) frequency capability.

While Synchrotrons have been used to provide THz frequency bandelectromagnetic radiation in ellipsometers, it is not remotely possibleto provide a Synchrotron at every location whereat it is desired topractice THz ellipsometry. The present invention provides combination ofmany elements, which results in a novel, practical system for generalapplication in the market place.

Before proceeding, it is of benefit to define some terminology. First, agenerally accepted range for what constitutes a Terahertz range offrequencies is from 3×10¹¹ (ie. 300 GHz), to 1.3×10¹² (ie. 1.3 Thz),Hertz. The Terahertz range is sandwiched between the microwave, (thehigh end of which has a wavelength of 1 millimeter), and thefar-infrared, (the long-wavelength edge of which is 100 micrometers),ranges of wavelengths/frequencies.

Next, it is noted that a number of sources of Terahertz (THz)electromagnetic radiation exit. For instance, a Smith-Purcell cell is adevice which directs an energetic beam of electrons very close to aruled surface of a diffraction grating. The effect on the trajectory ofthe beam is negligible, but a result is that Cherenkov radiation in theTerahertz frequency range can be created, where the phase velocity ofthe electromagnetic radiation is altered by the periodic grating.Another source of Terahertz radiation is a Free Electron Laser. In thissource a beam of electrons is accelerated to relativistic speed andcaused to pass through a periodic transverse magnetic field. The arrayof magnets is sometimes called an undulator or “wiggler” as it causesthe electrons to form a sinusoidal path. The acceleration of theelectrons causes release of photons, which is “synchrotron radiation”.Further, the electron motion is in phase with the field of said releasedelectromagnetic radiation, and therefore the fields add coherently.Instabilities in the electron beam resulting from interactions of theoscillations in the undulators lead to emission of electromagneticradiation, wherein electrons radiate independently. The wavelength ofthe emitted electromagnetic radiation from the electrons can be adjustedby adjusting the energy of the electron beam and/or magnetic fieldstrength of the undulators, to be in the Terahertz range. Another sourceof Terahertz frequencies is a Backward Wave Oscillator (BWO), which is avacuum tube system comprising an electron gun that generates an electronbeam and causes it to interact with an electromagnetic wave traveling ina direction opposite to that of ejected electrons such that THzfrequency oscillations are sustained by interaction between thepropagating traveling wave backwards against the electron beam.

It is also disclosed that numerous detectors exist for monitoringTerahertz range electromagnetic radiation. One example is a Golay cellwhich operates by converting a temperature change resulting fromelectromagnetic radiation impinging onto material, into a measurablesignal. Generally, when electromagnetic radiation is caused to impingeon a blackened material it heats a gas, (eg. Xenon) in an first chamberof an enclosure, and that causes a distortable reflecting diaphram/filmadjacent to said first chamber to change shape. In a second chamber,separated from the first by said diaphram/film an electromagnetic beamis caused to reflect from the film and into a photocell, which in turnconverts the received electromagnetic radiation into an electricalsignal. A Bolometer is another detector of monitoring Terahertz rangeelectromagnetic radiation, but operates by using the effect of achanging electric resistance caused by electromagnetic radiationimpinging onto a blackened metal.

It is also noted that there are Solid State sources and detectors ofTerahertz frequency electromagnetic radiation. For instance, anidentified reference by Nagashima et al. discloses that THz pulses canbe generated by a bow-tie photoconductive radiation antenna excited by amode-locked Ti-sapphire laser with 80 Fs time width pulses, and adetection antenna can be formed from a dipole-type photoconductiveantenna with a 5 micron gap fabricated on thin film LT-GaAs. Further, itis known that a company named AB Millimeter in Paris France, supplies asystem that covers the entire range from 8 GHz to 1000 GHz with solidstate source and detector devices.

With the above insight, it is disclosed that the present invention cancomprise an ellipsometer or polarimeter system which comprises aselection from the group consisting of:

-   -   a1) a source of electromagnetic radiation in functional        combination with a polarization state generator that provides        substantially polarized output in a frequency range between 300        GHz or lower and extending higher than at least 1 THz;    -   a2) a polarization state generator comprising a THz source of        electromagnetic radiation that provides substantially polarized        output in a frequency range between 300 GHz or lower and        extending higher than at least 1 THz;    -   b) a sample support;    -   c) at least one detector of electromagnetic radiation, said at        least one detector being capable of detecting electromagnetic        radiation in a range of between 300 GHz or lower and extending        higher than at least 1 THz.        Said ellipsometer or polarizer system further comprises, between        said THz source and said detector, at least one selection from        the group:    -   a stationary, rotatable or rotating polarizer between said THz        source and said sample support;    -   a stationary, rotatable or rotating analyzer between said sample        support and said detector;    -   a stationary, rotatable or rotating compensator between said        source and detector; and    -   an electro, acousto or opto-modulator;        the purpose thereof being to modulate a polarization state        during a data acquisition procedure.

It is noted that the polarization state generator comprising a THzsource of electromagnetic radiation that provides substantiallypolarized output in a frequency range between 300 GHz or lower andextending higher than at least 1 THz, utilizes natural polarizationprovided by the THz source and does not require use of a separatepolarizer; whereas said source of electromagnetic radiation infunctional combination with a polarization state generator that providessubstantially polarized output in a frequency range between 300 GHz orlower and extending higher than at least 1 THz, typically comprises aseparate polarizer.

Continuing, the THz source of electromagnetic radiation can comprise atleast one selection from the group consisting of:

-   -   a backward wave oscillator;    -   a Smith-Purcell cell;    -   a free electron laser; and    -   a solid state source device;        and preferably further comprises a frequency multiplier means        after said THz source of electromagnetic radiation, which        frequency multiplier receives electromagnetic radiation output        from said THz source, and provides harmonics of said        electromagnetic radiation in a range of between said source        output fundamental and about 1.6 THz.

Further, the ellipsometer or polarimeter system preferably comprises atleast one odd-bounce polarization state rotation system present between:

-   -   said THz source of electromagnetic radiation; and    -   said detector;        and comprises a method of its application in ellipsometer and        polarimeter and the like systems. This is beneficial in that it        eliminates the need to rotate an ellipsometer system Polarizer        to rotate a polarization state provided by the source of        electromagnetic radiation, optionally in combination with a        polarization state generator. The odd bounce optical image        rotating system is disclosed in U.S. Pat. No. 6,795,184 to        Herzinger et al. As described in said 184 Patent said odd bounce        serves optical image rotating system serves to rotate the        azimuthal angle of a linearly, or partially linearly polarized,        (ie. substantially polarized), beam of electromagnetic radiation        without entering significant deviation or displacement of the        propagation direction locus thereof, or significantly altering        the polarization state thereof, (ie. it does not cause        significant shifting of energy from a major intensity orthogonal        component into the other orthogonal component, or the shifting        of phase angle therebetween). The odd bounce optical image        rotating system can be described as a sequence of an odd number        of reflective elements oriented in a manner which causes an        entering beam of electromagnetic radiation to reflect from a        first thereof onto the second thereof and from the second        thereof onto the third thereof etc. For a three (3) reflective        element odd bounce optical image rotating element system, said        three reflections cause a beam of electromagnetic radiation to        emerge from the third reflective element with a rotated linear        or partially linear polarization azimuthal angle and in a        direction which is not significantly deviated or displaced from        the locus of the input beam, even when the odd bounce optical        image rotating system is caused to stepwise or continuously        rotate about an axis coincident with the locus of the beam of        electromagnetic radiation. The same is generally true for an odd        bounce optical image rotating element system comprising any odd        number, (eg. 3, 5, 7 etc.) of reflective elements. It is noted        that the greater the number of reflective elements the more        normal the angle of incidence a beam can make thereto, and        higher angles of incidence cause less aberration effects. Also,        where more than three reflection elements are present certain        non-idealities caused by the reflection elements can be canceled        by utilizing non-coincident coordinate systems for said        reflections. A trade-off, however, is that the greater the        number of reflective elements present, the more difficult it is        to align the system to avoid said beam deviation and        displacement.

Coupling the odd bounce optical image rotating system with asubstantially linear polarizing element, (which can comprise a source ofunpolarized electromagnetic radiation and a polarizer, or can comprise asource that provides polarized electromagnetic radiation at its output),provides a polarizer system in which the polarizing element can remainstationary while the azimuthal angle of the polarized beam ofelectromagnetism exiting therefrom, (as viewed from a position along thelocus of an electromagnetic beam caused to enter thereto), is rotated.

For general insight, it is also noted that a single three-hundred-sixty(360) degree rotation of a present invention odd bounce optical imagerotating element system about an axis coincident with a beam ofelectromagnetic radiation which functionally passes therethrough, causesseven-hundred-twenty (720) degrees of rotation of the major intensityorthogonal component. This is not of any critical consequence, but ismentioned as it must be taken into account during practice of presentinvention methodology.

The detector of electromagnetic radiation in a range between 300 GHz orlower and extending higher than 1 THz, can be a selection from the groupconsisting of:

-   -   a Golay cell;    -   a bolometer    -   a solid state detector.

Further, said ellipsometer or polarimeter system further comprises anFTIR source and a detector for detecting said FTIR frequency output in afrequency range above about 1 THz, and means for selecting between:

-   -   said THz source of electromagnetic radiation and optional        frequency multiplier that provides THz frequency output in a        range between 300 GHz or lower and extending higher than at        least 1 THz; and    -   said FTIR source that provides output in an IR frequency range        above about 1 THz.

The detector for detecting said FTIR frequency output in a frequencyrange above about 1 THz, and in which said detector of electromagneticradiation in a range between 300 GHz or lower and extending higher thanat least 1 THz, are each independently selected from the group:

-   -   a Golay cell;    -   a bolometer; and    -   a solid state detector.

As mentioned, in a preferred embodiment, the ellipsometer or polarimetersystem has output from said THz source, preferably with a frequencymultiplier in functional combination, so that it overlaps output fromsaid FTIR source in frequency, between at least 1.0 to 1.4 THz. Andpreferably said sources are calibrated such that substantially the sameresults, (eg. ellipsometric PSI and/or DELTA), are achieved by analyzingoutput from either of the selected detectors in the frequency range ofbetween about 1.0 to 1.4 THz.

In more detail, a preferred present invention ellipsometer orpolarimeter system comprises:

a selection from the group consisting of:

-   -   a1) an FTIR source of electromagnetic radiation in functional        combination with a polarization state generator, that provides        substantially polarized output in a frequency range above about        1 THz; and    -   a2) a polarization state generator comprising an FTIR source of        electromagnetic radiation which provides substantially polarized        output in a frequency range above about 1 THz;        and a selection from the group consisting of:    -   a3) a THz source of electromagnetic radiation in functional        combination with a polarization state generator, that provides        substantially polarized output in a frequency range between 300        GHz or lower and extending higher than at least 1 THz;    -   a4) a polarization state generator comprising a THz source of        electromagnetic radiation that provides substantially polarized        output in a frequency range between 300 GHz or lower and        extending higher than at least 1 THz;    -   wherein said THz source of electromagnetic radiation comprises        at least one selection from the group consisting of:        -   a backward wave oscillator;        -   a Smith-Purcell cell;        -   a free electron laser; and        -   a solid state device;    -   preferably in functional combination with a frequency multiplier        for providing harmonics of a fundamental output frequency that        provides substantially polarized frequency output in a frequency        range between 300 GHz or lower and extending higher than at        least 1 THz.

Further, said ellipsometer or polarimeter comprises means for selectingbetween said THz and FTIR sources.

Said ellipsometer or polarimeter further comprises:

-   -   b) a sample support;    -   c) a detector system of electromagnetic radiation comprising at        least one selection from the group consisting of:        -   a Golay cell detector;        -   a bolometer detector;        -   a solid state source device.            Said preferred ellipsometer or polarization system            embodiment further comprises at least one odd-bounce            polarization state rotation system present between:    -   said selected source; and    -   said selected detector.        And, said ellipsometer system further comprises, between said        selected source and said selected detector, at least one        selection from the group:    -   a stationary, rotatable or rotating polarizer between said THz        source and said sample support;    -   a stationary, rotatable or rotating analyzer between said sample        support and said detector;    -   a stationary, rotatable or rotating compensator between said        source and detector; and    -   an electro, acousto or opto-modulator.

In use a selected functional combination of selected source and selecteddetector is applied to cause electromagnetic radiation to impinge on andinteract with a sample on said sample support, then enter said selecteddetector, to the end that said detector produces an output.

Again, said preferred embodiment provides that the output from thefunctional combination of said selected THz source and preferably afrequency multiplier, and that from said FTIR source overlap infrequency between at least 1.0 to 1.4 THz such that substantially thesame results, (eg. ellipsometric PSI and/or DELTA), are achieved byanalyzing output from either of the selected detectors in the frequencyrange of between about 1.0 to 1.4 THz.

A preferred present invention system also comprises a chopper forchopping the electromagnetic beam which interacts with the sample. (Itis noted that FTIR Sources provide a natural “chopping” effect by way ofa moving mirror therewithin, hence, an added chopper is relevant onlywhen a THZ Source is selected). Further, a chopper is typically appliedwhen other elements are caused to rotate during data acquisition. Use ofa chopper enables noise reduction, particularly where data is obtainedwith the system located in a non-darkened room, such that spuriouselectromagnetic radiation is present.

A present invention method of characterizing a sample comprises thesteps of:

-   -   A) providing an ellipsometer or polarimeter as described above;    -   B) selecting a source and detector;    -   C) applying said selected source to cause substantially        polarized electromagnetic radiation to impinge on and interact        with said sample on said sample support, then proceed to and        enter said selected detector, to the end that said detector        provides output.

The present invention method also preferably involves chopping thesubstantially polarized electromagnetic radiation which is caused toimpinge on and interact with said sample on said sample support, andwhich then proceeds to and enters said selected detector, to the endthat said detector provides output based substantially only on thechopped beam content.

And, said method can further comprise performing at least one selectionfrom the group consisting of:

-   -   storing at least some output provided by said detector in        machine readable media;    -   analyzing at least some of the output provided by said detector        and storing at least some of the results of said analysis in        machine readable media;    -   displaying at least some output provided by said detector by        electronic and/or non-electronic means;    -   analyzing at least some of the output provided by said detector        and displaying at least some of the results of said analysis by        electronic and/or non-electronic means;    -   causing at least some output provided by said detector to        produce a signal which is applied to provide a concrete and        tangible result;    -   analyzing at least some of the output provided by said detector        and causing at least some thereof to produce a signal which is        applied to provide a concrete and tangible result.

Said method can further comprise the step of continuously or step-wiserotating at least one of the at least one odd-bounce polarization staterotation system present between said source and detector, or operating apresent electro, acousto or opto-modulator, during data acquisition.

The benefit is that, especially in ellipsometer/polarimeter etc. systemswhich operate in the IR range of wavelengths and below, it can bedifficult to cause rotation of a linear polarizer, (or analyzer),without adversely causing deviation of a beam of electromagneticradiation caused to pass therethrough, or causing mis-coordination ofmultiple elements thereof, (ie. multiple tipped wire linear polarizer asdescribed in U.S. Pat. No. 5,946,098). The present invention allowssetting fixed substantially linear polarizer, and analyzer azimuthalorientations, and using the odd bounce optical image rotating elementinstead, to effect different electromagnetic beam azimuthal rotationorientations.

It is also noted that various selected combinations of elements thatcomprise an ellipsometer or polarimeter, such as a specific selectionfrom:

-   -   a backward wave oscillator;    -   a Smith-Purcell cell;    -   a free electron laser; and    -   a solid state device;    -   preferably in functional combination with a frequency multiplier        for providing harmonics of a fundamental output frequency that        provides substantially polarized frequency output in a frequency        range between 300 GHz or lower and extending higher than at        least 1 THz;        and an FTIR Source;        in combination with selection from various types of Polarizers        and Analyzers and/or Compensators, as well as the motion of each        (ie. stationary, rotatable or rotating), and beam chopper        frequency during data acquisition;        in further functional combination with a specific selection        from:    -   a Golay cell detector;    -   a bolometer detector;    -   a solid state source device;        for each of the THz and IR ranges of operation, can provide        different quality or, for instance, ellipsometric PSI or DELTA        results, as quantified by measured Noise/Signal ratios, and        extent of wavelength range. As regards the later point, it is        noted that it can be advantageous to provide two THz sources        which provide different wavelength output and combine their        outputs.

At the time of this submittal it is believed that a preferred embodimentmakes use of a backward wave oscillator (BWO) in combination with amultiplier that provides x1, x2 x3 x6 and x9 capability, in functionalcombination with Golay cell or bolometer, provides good results in therange of from about 0.12-1.5 THz. Further, a conventional FTIR Source asused in a J. A. Woollam Co. IR-VASE (Reg. TM), to provide 10-150 THzcapability, has been shown capable of providing output down to about 1.0Thz. This beneficially allows an overlap between the THz and IR sourcesbetween about 1.0 and 1.4 Thz, which can be used for verification ofresults separately obtained using the THz and IR sources. In addition,it can be advantageous to cool a detector, (eg. by use of liquidhelium), and to adjust beam chopper rate, (eg. between about 12-50 Hz),differently for different source and detector combinations.

It is further believed that a present invention ellipsometer orpolarimeter system which comprises:

-   -   a2) a polarization state generator comprising a THz source of        electromagnetic radiation that provides substantially polarized        output in a frequency range between 300 GHz or lower and        extending higher than at least 1 THz; and        thereafter comprises at least one odd bounce optical image        rotating system which comprises:    -   an odd number of at least three reflective elements oriented        such that a beam of electromagnetic radiation provided by said        source of electromagnetic radiation interacts with each of said        at least three reflective elements of said at least one odd        bounce optical image rotating system and exits therefrom along a        non-deviated non-displaced trajectory, said beam of        electromagnetic radiation also interacting with a sample system        placed on said stage for supporting a sample system, and said        analyzer before entering said detector;        is definitely new and Patentable; particularly when it further        comprises at least two rotating elements, each thereof being        selected from the group consisting of:    -   a rotating polarizer between said source and said sample        supporting stage;    -   a rotating analyzer between said sample supporting stage and        said detector;    -   a rotating compensator between said source and said sample        supporting stage;    -   a rotating compensator between said sample supporting stage and        said detector;    -   a stokes vector selector between said source and said sample        supporting stage;    -   a stokes vector selector between said sample supporting stage        and said detector.

In addition, present invention methodology which involves which the stepof providing an ellipsometer or polarimeter system involves theselection of:

-   -   a2) a polarization state generator comprising a THz source of        electromagnetic radiation that provides substantially polarized        output in a frequency range between 300 GHz or lower and        extending higher than at least 1 THz; and        providing at least one odd bounce optical image rotating system        which comprises:    -   an odd number of at least three reflective elements oriented        such that a beam of electromagnetic radiation provided by said        source of electromagnetic radiation interacts with each of said        at least three reflective elements of said at least one odd        bounce optical image rotating system and exits therefrom along a        non-deviated non-displaced trajectory, said beam of        electromagnetic radiation also interacting with a sample system        placed on said stage for supporting a sample system, and said        analyzer before entering said detector;        is definitely new and Patentable.        This is the case wherein during data collection said odd-bounce        optical image rotating system is rotated as a selection from the        group consisting of:    -   step-wise; and    -   continuously rotated.        Additional basis of Patentability is more particularly provided        when the system comprises at least two rotating elements, each        thereof being selected from the group consisting of:    -   rotating polarizer;    -   rotating compensator;    -   rotating analyzer; and    -   said odd-bounce optical image rotating system;        and wherein said selected two rotating elements are both        continuously rotated during data acquisition.

It is also presented that an ellipsometer or polarimeter system whichoperates in the THz range, and its method of use, which ellipsometer orpolarimeter comprises a chopper to chop the electromagnetic beam andprovide substantially only the chopped electromagnetic beam to thedetector, and which is in functional combination with at least tworotating elements, each thereof being selected from the group consistingof:

-   -   rotating polarizer;    -   rotating compensator;    -   rotating analyzer; and    -   odd bounce optical image rotating system;        which are caused to rotate during data collection; is believed        to be new, novel and non-obvious. This is especially the case        where said THz range ellipsometer or polarimeter system        comprises at least one continuously rotating odd bounce optical        image rotating system comprising an odd number of at least three        reflective elements oriented such that a beam of electromagnetic        radiation provided by said source of electromagnetic radiation        interacts with each of said at least three reflective elements        of said at least one odd bounce optical image rotating system        and exits therefrom along a non-deviated non-displaced        trajectory, said beam of electromagnetic radiation also        interacting with a sample system placed on said stage for        supporting a sample system, and said analyzer before entering        said detector.

Continuing, the foregoing was substantially disclosed in Co-PendingPending application Ser. No. 12/456,791 Filed Jun. 23, 2009. In thefollowing, variations on the foregoing, substantially as disclosed inProvisional Application Ser. No. 61/281,905 Filed Nov. 22, 2009, arediscussed.

Much as in the foregoing, a present invention ellipsometer orpolarimeter system comprises:

-   -   a) a source selected from the group consisting of:        -   a1) an FTIR source (S2) of electromagnetic radiation in            functional combination with a polarization state generator,            that provides substantially polarized output in a frequency            range above about 1 THz; and        -   a2) a polarization state generator comprising an FTIR source            (S2) of electromagnetic radiation which provides            substantially polarized output in a frequency range above            about 1 THz.            One difference between that disclosed above, and what is now            disclosed, is that the presently disclosed system provides            that said polarization state generator is selected from the            group consisting of:    -   a21) a polarization state generator exit polarizer preceded by        an odd-bounce polarization state rotation system; and    -   a22) a polarization state generator exit polarizer preceded by a        polarization state generator entry polarizer.

As in the foregoing, a present invention ellipsometer or polarimetersystem further comprises:

and a source selected from the group consisting of:

-   -   a3) a THz source (S1) of electromagnetic radiation in functional        combination with a polarization state generator, that provides        substantially polarized output in a frequency range between 300        GHz or lower and extending higher than at least 1 THz.        Another difference between what was disclosed above and what is        now disclosed is that the presently disclosed system provides        that said polarization state generator is selected from the        group consisting of:    -   a4) a polarization state generator comprising a THz source (S1)        of electromagnetic radiation that provides substantially        polarized output in a frequency range between 300 GHz or lower        and extending higher than at least 1 THz, wherein said        polarization state generator is selected from the group        consisting of:        -   a41) a polarization state generator exit polarizer preceded            by an odd-bounce polarization state rotation system; and        -   a42) a polarization state generator exit polarizer preceded            by a polarization state generator entry polarizer.    -   As in the foregoing disclosure,        -   said THz source (S1) of electromagnetic radiation comprising            at least one selection from the group consisting of:            -   a backward wave oscillator (BWO);            -   a Smith-Purcell cell (SP); and            -   a free electron laser (FE);        -   optionally in functional combination with a frequency            multiplier (M) for providing harmonics of a fundamental            output frequency that provides substantially polarized            frequency output in a frequency range between 300 GHz or            lower and extending higher than at least 1 THz, and    -   said ellipsometer or polarimeter system further comprising means        for selecting between said THz (S1) and FTIR (S2) sources.

This is followed by:

-   -   b) a sample (S) support;    -   c) a detector system (D1) (D2) (D3) of electromagnetic radiation        comprising at least one selection from the group consisting of:        -   a golay cell (GC) detector; and        -   a bolometer (BOL) detector.            And said ellipsometer or polarimeter system again further            comprises, between said selected source and said selected            detector, at least one selection from the group:    -   a stationary, rotatable or rotating polarizer (P) between said        source (S1) (S2) and said sample (S) support;    -   a stationary, rotatable or rotating analyzer (A) between said        sample support (S) and said detector (GC) (BOL); and    -   a stationary, rotatable or rotating compensator (C) (C′) between        said source (S) and detector (GC) (BOL).        In use a selected functional combination of selected source,        optional polarization state generator, and detector is applied        to cause electromagnetic radiation to pass impinge on and        interact with a sample on said sample support (S), then enter        said selected detector (D1) (D2) (D3), to the end that said        detector produces an output.

A specific presently disclosed invention is found where the A2polarization state generator comprises an FTIR source (S2), and the A4polarization state generator comprises a THz source (S1), wherein a22and a42 are further elected.

Another presently disclosed invention is found where the A2 polarizationstate generator comprises an FTIR source (S2), and the A4 polarizationstate generator comprises a THz source (S1), wherein a21 and a41 arefurther elected.

Another presently disclosed invention is found where the A2 polarizationstate generator comprises an FTIR source (S2), and the A4 polarizationstate generator comprises a THz source (S1), wherein a21 and a42 arefurther elected.

Another presently disclosed invention is found where the A2 polarizationstate generator comprises an FTIR source (S2), and the A4 polarizationstate generator comprises a THz source (S1), wherein a22 and a41 arefurther elected.

A method of characterizing a sample comprising the steps of:

-   -   A) providing an ellipsometer or polarimeter system as Just        disclosed;    -   B) selecting a source and detector and polarization state        generator;    -   C) applying said selected source to cause substantially        polarized electromagnetic radiation to impinge on and interact        with said sample (S) on said sample support, then proceed to and        enter said selected detector, to the end that said detector        provides output;        said method further comprising performing at least one selection        from the group consisting of:    -   storing at least some output provided by said detector in        machine readable media;    -   analyzing at least some of the output provided by said detector        and storing at least some of the results of said analysis in        machine readable media;    -   displaying at least some output provided by said detector by        electronic and/or non-electronic means;    -   analyzing at least some of the output provided by said detector        and displaying at least some of the results of said analysis by        electronic and/or non-electronic means;    -   causing at least some output provided by said detector to        produce a signal which is applied to provide a concrete and        tangible result;    -   analyzing at least some of the output provided by said detector        and causing at least some thereof to produce a signal which is        applied to provide a concrete and tangible result.

Another recitation of a presently disclosed invention is that it is anellipsometer or polarimeter system comprising:

-   -   a) a source of electromagnetic radiation that provides at least        partially polarized output in a frequency range between 1.1 THz        or lower and extending to 1.4 THZ or higher; and    -   b) a polarization state generator consisting of a series        combination of a exit polarization state generator polarizer        preceded by a selection from the group consisting of:        -   an entry polarization state generator polarizer; and        -   an odd-bounce polarization state rotation system.            This is followed by:    -   c) a sample support; and    -   d) at least one detector of electromagnetic radiation, said at        least one detector being capable of detecting electromagnetic        radiation in a range of between 300 GHz or lower and extending        up at least 1.4 THZ.        Between said source and said detector, there is also present at        least one selection from the group:    -   a stationary, rotatable or rotating polarizer between said THZ        source and said sample support;    -   a stationary, rotatable or rotating analyzer between said sample        support and said detector;    -   a stationary, rotatable or rotating compensator between said        source and detector;        in addition to said polarization state generator components.

It is noted that the polarization state generator characterized by aselected odd-bounce polarization state rotation system followed by saidpolarization state generator exit polarizer operates by the odd-bouncepolarization state generator receiving an at least partially polarizedbeam of electromagnetic radiation from the source thereof, rotating thepolarization state of said at least partially polarized beam and andpassing it through said polarization state exit polarizer which servesto improve the purity of the polarization state exiting therefrom.

It is also noted that the polarization state generator is characterizedby a polarization state generator entry polarizer followed by saidpolarization state generator exit polarizer operates by the polarizationstate generator entry polarizer receiving an at least partiallypolarized beam of electromagnetic radiation from the source thereof andthen passing it through said polarization state exit polarizer. Saidpolarization state generator entry polarizer serves to enable avoiding acondition wherein an effective azimuth of the at least partiallypolarized beam of electromagnetic radiation provided by the sourcethereof, and that of the polarization state generator exit polarizerpresent at essentially 90 degrees with respect to one another therebypreventing the at least partially polarized beam of electromagneticradiation from progressing beyond the polarization state generator exitpolarizer.

Another recitation of a present invention ellipsometer or polarimetersystem provides that it comprise:

-   -   a) a THZ source of electromagnetic radiation that provides at        least partially polarized output in a frequency range between        300 GHz or lower and extending to 1.1 THZ or higher; and    -   b) a polarization state generator consisting of a series        combination of a exit polarization state generator polarizer        preceded by a selection from the group consisting of:        -   an entry polarization state generator polarizer; and        -   an odd-bounce polarization state rotation system.            Said elements are followed by;    -   c) a sample support; and    -   d) at least one detector of electromagnetic radiation, said at        least one detector being capable of detecting electromagnetic        radiation in a range of between 300 GHz or lower and extending        up at least 1.1 THZ.        In addition to said polarization state generator components,        said ellipsometer or polarimeter system further comprises,        between said source and said detector, at least one selection        from the group:    -   a stationary, rotatable or rotating polarizer between said        source and said sample support;    -   a stationary, rotatable or rotating analyzer between said sample        support and said detector;    -   a stationary, rotatable or rotating compensator between said        source and detector.

Another recitation of a present invention ellipsometer or polarimetersystem provides that it comprise:

-   -   a) an FTIR source of electromagnetic radiation that provides at        least partially polarized output in a frequency range between        1.1 THz or lower and extending to 1.4 THZ or higher:    -   b) a polarization state generator consisting of a series        combination of a exit polarization state generator polarizer        preceded by a selection from the group consisting of:        -   an entry polarization state generator polarizer; and        -   an odd-bounce polarization state rotation system.            Said ellipsometer or polarimeter system then further            comprises:    -   c) a sample support; and    -   d) at least one detector of electromagnetic radiation, said at        least one detector being capable of detecting electromagnetic        radiation in a range of between 1.1 THz or lower and extending        up at least 1.4 THZ.        In addition to said polarization state generator components,        said ellipsometer or polarimeter system further comprises,        between said source and said detector, at least one selection        from the group:    -   a stationary, rotatable or rotating polarizer between said THZ        source and said sample support;    -   a stationary, rotatable or rotating analyzer between said sample        support and said detector;    -   a stationary, rotatable or rotating compensator between said        source and detector.

Continuing, the present invention ellipsometer and polarimeter systemcan be configured as a Rotating Analyzer, a Rotating Polarizer or aRotating Compensator system. The preprint paper in the BackgroundSection discloses a Rotating Analyzer system. Reference to FIG. 1 pshows that present invention Rotating Analyzer ellipsometer orpolarimeter system sequentially comprises:

-   -   a backward wave oscillator (BWO);    -   a focusing lens;    -   a rotatable image rotation system;    -   a rotatable wire grid polarizer;    -   a sample supporting stage;    -   a rotating analyzer;    -   a Golay cell;        said ellipsometer or polarimeter system further comprising:    -   an optical chopper;        between said backward wave oscillator and said Golay cell.        In use a polarized beam of Terahertz spectral range        electromagnetic radiation is provided by said backward wave        oscillator, is focused by the focusing lens, has its        polarization state rotated by said rotatable image rotation        system and passes through said rotatable wire grid polarizer,        then impinges on a sample placed on said sample supporting        stage, reflects therefrom and passes through said rotating        analyzer and enters said Golay cell. Said Rotating Analyzer        ellipsometer or polarimeter system is distinguished in that,        during data acquisition, the rotatable image rotation system and        rotatable wire grid polarizer are functionally stepwise rotated        in tandum, wherein said rotatable wire grid polarizer is        stepwise rotated through a sequence of angles twice that of the        rotatable image rotation system, such that the polarization        state of the beam provided to the wire grid polarizer by the        rotatable image rotation system, is passed by said rotatable        wire grid polarizer even where the polarization state of the        polarized beam of Terahertz spectral range electromagnetic        radiation from the backward wave oscillator is rotated by 90        degrees.

Said Rotating Analyzer ellipsometer or polarimeter system can becharacterized by said rotatable image rotation system being an oddbounce (OB) (OB′) optical image rotating system comprising an odd numberof at least three reflective elements oriented such that a beam ofelectromagnetic radiation provided by said source of electromagneticradiation interacts with each of said at least three reflective elementsof said at least one odd bounce optical image rotating system and exitstherefrom along a non-deviated non-displaced trajectory, said beam ofelectromagnetic radiation also interacting with a sample system placedon said stage for supporting a sample system, and said analyzer beforeentering said detector, and the at least one odd bounce (OB) (OB′)optical image rotating system can consist of a selection from the groupconsisting of:

-   -   three; and    -   five;        reflective elements.

Said present invention Rotating Analyzer ellipsometer or polarimetersystem can further comprise at least one beam directing reflecting meansand the sample supporting stage can be part of a 20 goniometer.

A variation on the present invention Rotating Analyzer ellipsometer orpolarimeter system can sequentially comprise:

-   -   a backward wave oscillator (BWO);    -   optionally a focusing lens;    -   a rotatable image rotation system;    -   a rotatable wire grid polarizer;    -   a sample supporting stage;    -   a rotating analyzer;    -   a Golay cell.        Said ellipsometer or polarimeter system further comprises:    -   an optical chopper;        between said backward wave oscillator and said Golay cell.

In use a polarized beam of Terahertz spectral range electromagneticradiation is provided by said backward wave oscillator, is optionallyfocused by the focusing lens, has its polarization state rotated by saidrotatable image rotation system and passes through said rotatable wiregrid polarizer, then impinges on a sample placed on said samplesupporting stage, reflects therefrom and passes through said rotatinganalyzer and enters said Golay cell.

Said ellipsometer or polarimeter system is distinguished in that, duringdata acquisition, the rotatable image rotation system and rotatable wiregrid polarizer are functionally stepwise rotated in tandum, wherein saidrotatable wire grid polarizer is stepwise rotated through a sequence ofangles twice that of the rotatable image rotation system, such that thepolarization state of the beam provided to the wire grid polarizer bythe rotatable image rotation system, is passed by said rotatable wiregrid polarizer even where the polarization state of the polarized beamof Terahertz spectral range electromagnetic radiation from the backwardwave oscillator is rotated by 90 degrees.

Said ellipsometer or polarimeter system can involve a rotatable imagerotation system which is an odd bounce (OB) (OB′) optical image rotatingsystem comprising an odd number of at least three reflective elementsoriented such that a beam of electromagnetic radiation provided by saidsource of electromagnetic radiation interacts with each of said at leastthree reflective elements of said at least one odd bounce optical imagerotating system and exits therefrom along a non-deviated non-displacedtrajectory, said beam of electromagnetic radiation also interacting witha sample system placed on said stage for supporting a sample system, andsaid analyzer before entering said detector.

Said ellipsometer or polarimeter system at least one odd bounce (OB)(OB′) optical image rotating system can consist of a selection from thegroup consisting of:

-   -   three; and    -   five;        reflective elements.

Said ellipsometer or polarimeter system can further comprise at leastone beam directing reflecting means.

Said ellipsometer or polarimeter system can involve a sample supportingstage is part of a system for controlling the angle of incidence atwhich a beam of electromagnetic radiation is caused to approach saidsample.

Another recitation of a rotating analyzer ellipsometer or polarimetersystem provides that it can sequentially comprise:

-   -   a backward wave oscillator (BWO);    -   optionally a focusing lens;    -   a rotatable first wire grid polarizer;    -   a rotatable second wire grid polarizer;    -   a sample supporting stage;    -   a rotating analyzer;    -   a Golay cell.        Said ellipsometer or polarimeter system further comprises:    -   an optical chopper;        between said backward wave oscillator and said Golay cell.

In use a polarized beam of Terahertz spectral range electromagneticradiation is provided by said backward wave oscillator, is optionallyfocused by the focusing lens, has its polarization state altered by saidfirst rotatable wire grid polarizer and then by said second rotatablewire grid polarizer, then impinges on a sample placed on said samplesupporting stage, reflects therefrom and passes through said rotatinganalyzer and enters said Golay cell.

Said ellipsometer or polarimeter system is distinguished in that saidtwo rotatable wire grid polarizers are functionally operated in tandumsuch that the polarization state of the beam provided to the secondrotatable wire grid polarizer by the first rotatable wire gridpolarizer, is passed by said second rotatable wire grid polarizer, whereit not be passed were the first rotatable wire grid polarizer notpresent and the polarization state of the polarized beam of Terahertzspectral range electromagnetic radiation from the backward waveoscillator is rotated by 90 degrees at the location of said sample.

Said ellipsometer or polarimeter system can further comprise at leastone beam directing reflecting means.

Said ellipsometer or polarimeter system can involve a sample supportingstage is part of a system for controlling the angle of incidence atwhich a beam of electromagnetic radiation is caused to approach saidsample.

FA

A fixed analyzer ellipsometer or polarimeter system can sequentiallycomprise:

-   -   a backward wave oscillator (BWO);    -   optionally a focusing lens;    -   optionally a rotatable or rotating polarizer;    -   a sample supporting stage;    -   a rotatable image rotation system;    -   a fixed position analyzer;    -   a Golay cell.        Said ellipsometer or polarimeter system further comprising:    -   an optical chopper;        between said backward wave oscillator and said Golay cell.

In use a polarized beam of Terahertz spectral range electromagneticradiation is provided by said backward wave oscillator, is optionallyfocused by the focusing lens, optionally has its polarization staterotated by said rotatable or rotating polarizer, then impinges on asample placed on said sample supporting stage, reflects therefrom andpasses through said rotatable image rotation system and fixed positionanalyzer and enters said Golay cell.

Said ellipsometer or polarimeter system is distinguished in that, duringdata acquisition, the rotatable image rotation system is stepwiserotated while the analyzer remains fixed in position.

A present invention Rotating Polarizer ellipsometer or polarimetersystem sequentially can comprise:

RP

-   -   a backward wave oscillator (BWO);    -   optionally a focusing lens;    -   a rotatable or rotating polarizer;    -   a sample supporting stage;    -   a rotatable image rotation system;    -   a rotatable wire grid analyzer;    -   a Golay cell.        Said ellipsometer or polarimeter system can further comprise:    -   an optical chopper;        between said backward wave oscillator and said Golay cell.

In use a polarized beam of Terahertz spectral range electromagneticradiation is provided by said backward wave oscillator, is optionallyfocused by the focusing lens, has its polarization state rotated by saidrotatable or rotating polarizer, then impinges on a sample placed onsaid sample supporting stage, reflects therefrom and passes through saidrotatable image rotation system and rotatable wire grid analyzer andenters said Golay cell.

Said ellipsometer or polarimeter system is distinguished in that, duringdata acquisition, the rotatable image rotation system and rotatable wiregrid analyzer are functionally stepwise rotated in tandum, wherein saidrotatable wire grid analyzer is stepwise rotated through a sequence ofangles twice that of the rotatable image rotation system, such that thepolarization state of the beam provided to the rotatable wire gridanalyzer by the rotatable image rotation system.

Said ellipsometer or polarimeter system can involve a rotatable imagerotation system is an odd bounce (OB) (OB′) optical image rotatingsystem comprising an odd number of at least three reflective elementsoriented such that a beam of electromagnetic radiation provided by saidsource of electromagnetic radiation interacts with each of said at leastthree reflective elements of said at least one odd bounce optical imagerotating system and exits therefrom along a non-deviated non-displacedtrajectory, said beam of electromagnetic radiation also interacting witha sample system placed on said stage for supporting a sample system, andsaid analyzer before entering said detector.

Said at least one odd bounce (OB) (OB′) optical image rotating systemcan consist of a selection from the group consisting of:

-   -   three; and    -   five;        reflective elements.

Said ellipsometer or polarimeter system can further comprise at leastone beam directing reflecting means.

Said ellipsometer or polarimeter system can provide that the samplesupporting stage is part of a system for controlling the angle ofincidence at which a beam of electromagnetic radiation is caused toapproach said sample.

A present invention Rotating Compensator ellipsometer or polarimetersystem sequentially comprising:

RC

-   -   a backward wave oscillator (BWO);    -   optionally a focusing lens;    -   a rotatable image rotation system;    -   a rotatable wire grid polarizer;    -   a sample supporting stage;    -   a rotatable analyzer;    -   a Golay cell.        Said ellipsometer or polarimeter can system further comprise:    -   an optical chopper; and    -   a rotating compensator;        between said backward wave oscillator and said Golay cell.

In use a polarized beam of Terahertz spectral range electromagneticradiation is provided by said backward wave oscillator, is optionallyfocused by the focusing lens, has its polarization state rotated by saidrotatable image rotation system and passes through said rotatable wiregrid polarizer, then impinges on a sample placed on said samplesupporting stage, reflects therefrom and passes through said rotatableanalyzer; said Terahertz spectral range electromagnetic radiation alsopassing through said optical chopper and rotating compensator; andenters said Golay cell.

Said ellipsometer or polarimeter system is distinguished in that, duringdata acquisition while said rotating compensator is caused tocontinuously rotate, the rotatable image rotation system and rotatablewire grid polarizer are functionally stepwise rotated in tandum, whereinsaid rotatable wire grid polarizer is stepwise rotated through asequence of angles twice that of the rotatable image rotation system,such that the polarization state of the beam provided to the wire gridpolarizer by the rotatable image rotation system, is passed by saidrotatable wire grid polarizer even where the polarization state of thepolarized beam of Terahertz spectral range electromagnetic radiationfrom the backward wave oscillator is rotated by 90 degrees

Said ellipsometer or polarimeter system can provide that the rotatableanalyzer is optionally also stepwise rotated during data acquisition.

Said ellipsometer or polarimeter system can provide that said rotatableimage rotation system is an odd bounce (OB) (OB′) optical image rotatingsystem comprising an odd number of at least three reflective elementsoriented such that a beam of electromagnetic radiation provided by saidsource of electromagnetic radiation interacts with each of said at leastthree reflective elements of said at least one odd bounce optical imagerotating system and exits therefrom along a non-deviated non-displacedtrajectory, said beam of electromagnetic radiation also interacting witha sample system placed on said stage for supporting a sample system, andsaid analyzer before entering said detector.

Said at least one odd bounce (OB) (GB′) optical image rotating systemconsists of a selection from the group consisting of:

-   -   three; and    -   five;        reflective elements.

Said ellipsometer or polarimeter system can further comprise at leastone beam directing reflecting means.

Said ellipsometer or polarimeter system can provide that the samplesupporting stage is part of a system for controlling the angle ofincidence at which a beam of electromagnetic radiation is caused toapproach said sample.

Said ellipsometer or polarimeter system can provide that the rotatingcompensator is present at a selection from the group consisting of:

-   -   between the backward wave oscillator and said sample supporting        stage; and    -   said sample supporting stage and said Golay Cell;        and which further comprises a linear polarizer on the same side        of the sample stage as is the rotating compensator.

GENERALIZED DISCLOSURE

As further, generalized, disclosure it is presented that a TeraHertzEllipsometer can be configured from components:

Sources

-   -   SOURCE 1=Generalized narrow-band essentially single frequency:        -   Backward wave oscillator;        -   Backward wave oscillator with multipliers;        -   Multiple Backward wave oscillators;        -   Smith Purcell;        -   Free Electron;        -   Mixed-laser-beat+Solid State Emitter    -   SOURCE 2=Generally Broadband Blackbody dominated:        -   Globar;        -   Nerst Glower;        -   Arc Lamp.

Frequency Purification Systems

THZ Filter 1+Narrow Pass THZ Filter

-   -   Tunable Diffraction Grating;    -   Tunable Interferometer;    -   Dispersive Prism;

THZ Filter 2+Order Sorting

-   -   Longpass Absorption Filter;    -   Shortpass Absorption Filter;    -   Bandpass Absorption Filter;

THZ Filter 3

-   -   at least one, perhaps more, combination from each of the THZ        Filter 1 and THZ Filter 2 categories.

Detectors

-   -   DET 1=        -   Golay Cell;        -   Cryogenic Bolomete;        -   Intensity sensitive Solid State Device;    -   DET 2=        -   direct Electric Field Sensitive Solid State Device; (for use            with mixed laser Source)    -   DET 3=        -   Combination of DET 1 and DET 2

Polarization Optical Element for Lock-in Measurements

-   -   Changing and element, (stepwise of continuous), provides        synchronization to:        -   Rotating Analyzer (RA);        -   Rotating Polarizer (RP);        -   Rotating Compensator (RC);        -   Stokes Vector Control (ISVC)            -   (used only with Source 1).

From the above elements two types of THZ Ellipsometer Systems can beconfigured, namely:

-   -   a Scanning Monochromator-like System; and    -   a Dual System providing Scanning+FTIR System.

Systems which can be Constructed from the Above Elements are

Scanning Monochromator

-   -   REQUIRED SOURCE 1    -   OPTIONAL THZ FILTER 3    -   Optional BEAM CHOPPER        -   (Beam Chopped if more than one RA/RP/RC element continuously            rotated during data acquisition)    -   OPTIONAL Fixed Stokes vector Setting Sub-System (ie. Polarizer        or Partial Polarizer);    -   OPTIONAL Polarizer Rotator between Source and Detector;    -   REQUIRED RP and/or RA and/or RC and/or 2nd RC and/or    -   ISVC and/or 2nd ISVC;    -   REQUIRED Sample Stage with Reflection and/or    -   Transmission capability;    -   OPTIONAL Variable Angle capability;    -   OPTIONAL 2nd Polarization Rotator between Source and Detector;    -   OPTIONAL Fixed Stokes Vector Detecting Sub System (ie. Polarizer        or Partial Polarizer);    -   OPTIONAL THZ Filter 3;    -   REQUIRED Detector 1.

Dual System: Scanning+FTIR System

-   -   REQUIRED Source 1+    -   OPTIONAL THZ Filter 3; and    -   REQUIRED Source 2 and FTIR Modulating System; and    -   OPTIONAL Chopper (Beam Chopped if more than one RA/RP/RC element        continuously rotated during data acquisition);    -   OPTIONAL Fixed Stokes Vector Setting Sub-System (ie. Polarizer        or Partial Polarizer); (eg. in common or separate for Source 1        and Source 2 beam paths);    -   OPTIONAL Polarization Rotator between Source and Detector; (eg.        in common or separate for Source 1 and Source 2 beam paths);    -   OPTIONAL ISVC; (used only with RP and/or RA and/or RC and/or        second RC; (eg. in common or separate for Source 1 and Source 2        beam paths);    -   Required Sample Stage; (with Reflection and/or Transmission        capability;    -   OPTIONAL Variable Angle capability, common or nearly common        measurement spot on Sample, but not necessarily at same Angle of        Incidence);    -   OPTIONAL 2nd Pol Rotator between Source and Detector; (eg. in        common or separate for Source 1 and Source 2 beam paths);    -   OPTIONAL Fixed Stokes Vector Detecting Sub System (ie. Polarizer        or Partial Polarizer); (eg. in common or separate for Source 1        and Source 2 beam paths);    -   OPTIONAL THZ Filter 3; (eg. in common or separate for Source 1        and Source 2 beam paths);    -   REQUIRED Detector 3 for use with Source 1; and    -   REQUIRED Detector 1 for use with Source 2; (eg. in common or        separate for Source 1 and Source 2 beam paths).

The foregoing outline provides basis for describing specific presentinvention systems.

First, a scanning monochromator system for application in the Tetrahertzfrequency range, can comprise:

a narrow-band essentially single frequency source selected from thegroup consisting of:

-   -   a Backward wave oscillator;    -   a Backward wave oscillator with multipliers;    -   a Multiple Backward wave oscillators;    -   a Smith Purcell;    -   a Free Electron;    -   a Mixed-laser-beat+Solid State Emitter;        and a detector selected from the group consisting of:    -   Golay Cell;    -   Cryogenic Bolometer;    -   Intensity sensitive Solid State Device;        between said narrow-band essentially single frequency source and        said detector, there being a sample supporting stage with        reflection and/or transmission capability;        said scanning monochromater system further comprising, between        said narrow-band essentially single frequency source and said        detector at least one component which is caused to rotate during        use, and which is selected from the group consisting of:    -   a rotating polarizer between said source and said sample        supporting stage;    -   a rotating analyzer between said sample supporting stage and        said detector;    -   a rotating compensator between said source and said sample        supporting stage;    -   a rotating compensator between said sample supporting stage and        said detector;    -   a stokes vector selector between said source and said sample        supporting stage;    -   a stokes vector selector between said sample supporting stage        and said detector;        such that in use a sample is placed on said sample supporting        stage and a beam of electromagnetic radiation provided by said        selected source is caused to interact with said sample, then        enter said selected detector.

Said scanning monochromator system can further comprise at least oneselection from the group:

-   -   a fixed stokes vector setting polarizer or partial polarizer        between said narrow-band essentially single frequency source and        said sample supporting stage;    -   a fixed stokes vector setting polarizer or partial polarizer        between said sample supporting stage and said selected detector.

Said scanning monochromator system can further comprise at least onepolarization state rotating system between said selected source andselected detector.

Said scanning monochromator system can comprise two polarization staterotating systems between said selected source and selected detector.

Said scanning monochromator system can further comprise a beam chopper,said beam chopper being applied to chop said beam of electromagneticradiation during use.

Said scanning monochromator system can, during use, cause saidelectromagnetic beam to be chopped by said beam chopper while twoelements selected from the group consisting of:

-   -   a rotating polarizer between said source and said sample        supporting stage;    -   a rotating analyzer between said sample supporting stage and        said detector;    -   a rotating compensator between said source and said sample        supporting stage;    -   a rotating compensator between said sample supporting stage and        said detector;    -   a stokes vector selector between said source and said sample        supporting stage;    -   a stokes vector selector between said sample supporting stage        and said detector;        are caused to rotate.

Said scanning monochromator system can further comprise means forcontrolling the angle of incidence at which said beam of electromagneticradiation from said selected source approaches said sample.

Said scanning monochromator system can further comprise, between saidselected source and selected detector, at least one terahertz filter andnarrow pass THZ filter selected from the group:

-   -   Tunable Diffraction Grating;    -   Tunable Interferometer;    -   Dispersive Prism;        and/or        at least one THZ filter and order sorting filter selected from        the group consisting of:    -   Longpass Absorption Filter;    -   Shortpass Absorption Filter;    -   Bandpass Absorption Filter.

Said scanning monochromator system can further comprise a rotatablepolarizer, the rotation of which is synchronized to that of the said atleast one polarization state rotating system between said selectedsource and selected detector.

Said scanning monochromator system can further comprise a lock-in systemreferenced to said at least one component selected from the group ofsaid:

-   -   rotating polarizer between said source and said sample        supporting stage;    -   rotating analyzer between said sample supporting stage and said        detector;    -   rotating compensator between said source and said sample        supporting stage;    -   rotating compensator between said sample supporting stage and        said detector;    -   stokes vector selector between said source and said sample        supporting stage;    -   stokes vector selector between said sample supporting stage and        said detector;        for synchronizing the operation thereof to said at least one        detector selected from the group consisting of said:    -   Golay Cell;    -   Cryogenic Bolometer;    -   Intensity sensitive Solid State Device;

Another present invention system is a dual scanning and FTIR system forapplication in the Terahertz and Infrared frequency range, comprising:

-   -   a source for providing Thz range electromagnetic radiation        selected from the group consisting of:        -   a backward wave oscillator;        -   a backward wave oscillator with multipliers;        -   multiple Backward wave oscillators;        -   a Smith Purcell;        -   a free electron; and        -   a mixed-laser-beat+solid state emitter;            said dual scanning and FTIR system further comprising a            source for providing generally broadband blackbody range            electromagnetic radiation selected from the group consisting            of:    -   a Globar source;    -   a Nerst Glower source;    -   an arc lamp source;        in functional combination with a FTIR modulating system;        said dual scanning and FTIR system further comprising at least        one detector selected from the group consisting of    -   a Golay Cell;    -   a cryogenic bolometer;    -   an intensity sensitive solid state device;    -   a direct electric field sensitive solid state device;        said dual scanning and FTIR system further comprising at least        one selection from the group consisting of:    -   a rotating analyzer;    -   a rotating polarizer; and    -   at least one rotating compensator;        and a sample supporting stage with reflection and/or        transmission capability between said selected sources and said        selected detector.

Said dual scanning and FTIR system for application in the Terahertz andInfrared frequency range can further comprise, in combination with theselected source for providing Thz range electromagnetic radiation whichis selected from the group consisting of:

-   -   a backward wave oscillator;    -   a backward wave oscillator with multipliers;    -   multiple Backward wave oscillators;    -   a Smith Purcell;    -   a free electron; and    -   a mixed-laser-beat+solid state emitter;

at least one selection from the group consisting of:

-   -   a tunable diffraction grating;    -   a tunable interferometer;    -   a dispersive prism;

and/or

at least one selection from the group consisting of:

-   -   a longpass Absorption Filter;    -   a shortpass Absorption Filter;    -   a bandpass Absorption Filter.

Said dual scanning and FTIR system for application in the Terahertz andInfrared frequency range can further comprise a fixed stokes vectorsetting sub-system polarizer or partial polarizer positioned in the pathof at least one electromagnetic beam from a selection from the groupconsisting of:

-   -   said selected source for providing Thz range electromagnetic        radiation; and    -   said FTIR source.

Said dual scanning and FTIR system can further comprise a second fixedstokes vector setting sub-system polarizer or partial polarizerpositioned in the path of at least one electromagnetic beam from aselection from the group consisting of:

-   -   said selected source for providing Thz range electromagnetic        radiation; and    -   said FTIR source.

Said dual scanning and FTIR system for application in the Terahertz andInfrared frequency range can further comprise at least two rotatingelements, selected from the group:

-   -   rotating polarizer and rotating analyzer;    -   rotating polarizer and rotating compensator;    -   rotating analyzer and rotating compensator;    -   two rotating compensators;

Said dual scanning and FTIR system for application in the Terahertz andInfrared frequency range can further comprise an ISVC fixed stokesvector control selecting sub-system polarizer or partial polarizerpositioned in the path of at least one electromagnetic beam from aselection from the group consisting of:

-   -   said selected source for providing Thz range electromagnetic        radiation; and    -   said FTIR source.

Said dual scanning and FTIR system for application in the Terahertz andInfrared frequency range can further comprise at least one polarizationstate rotating system between said selected source and selected detectorpositioned in the path of at least one electromagnetic beam from aselection from the group consisting of:

-   -   said selected source for providing Thz range electromagnetic        radiation; and    -   said FTIR source.

Said dual scanning and FTIR system for application in the Terahertz andInfrared frequency range can further comprise a second polarizationstate rotating system between said selected source and selected detectorpositioned in the path of at least one electromagnetic beam from aselection from the group consisting of:

-   -   said selected source for providing Thz range electromagnetic        radiation; and    -   said FTIR source.

Said dual scanning and FTIR system can, during use, provide that saidelectromagnetic beam is caused to be chopped by a beam chopper while twoelements selected from the group consisting of:

-   -   a rotating polarizer between said source and said sample        supporting stage;    -   a rotating analyzer between said sample supporting stage and        said detector;    -   a rotating compensator between said source and said sample        supporting stage;    -   a rotating compensator between said sample supporting stage and        said detector;    -   a stokes vector selector between said source and said sample        supporting stage;    -   a stokes vector selector between said sample supporting stage        and said detector;        are present and are caused to rotate.

Said dual scanning and FTIR system can further comprise means forcontrolling the angle of incidence at which said beam of electromagneticradiation from said selected source approaches said sample.

Said scanning monochromator system can further comprise a rotatablepolarizer, the rotation of which is synchronized to that of the said atleast one polarization state rotating system between said selectedsource and selected detector.

Said dual scanning and FTIR system can further comprise a lock-in systemreferenced to said at least one component selected from the group:

-   -   rotating polarizer between said source and said sample        supporting stage;    -   rotating analyzer between said sample supporting stage and said        detector;    -   rotating compensator between said source and said sample        supporting stage;    -   rotating compensator between said sample supporting stage and        said detector;    -   stokes vector selector between said source and said sample        supporting stage;    -   stokes vector selector between said sample supporting stage and        said detector;        for synchronizing the operation thereof to said at least one        detector selected from the group consisting of said:    -   a Golay Cell;    -   a cryogenic bolometer;    -   an intensity sensitive solid state device;    -   a direct electric field sensitive solid state device.        It is to be appreciated that a preferred source of THZ        electromagnetic radiation is of a non-laser type.

The present invention will be better understood by reference to theDetailed Description Section of this Specification, in combination withthe Drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a-1 c show demonstrative configurations for a present inventionellipsometer or polarimeter system.

FIG. 1 d shows an alternative polarization state generator involving amodulator.

FIGS. 1 e-1 g show systems similar to those in FIGS. 1 a-1 c, with therelative positions of the Odd Bounce image rotation system and Polarizerreversed.

FIG. 1 h indicate that the Odd Bounce image rotation system Polarizerreversed are controlled in synchrony.

FIGS. 1 i-1 k are similar to FIGS. 1 e-1 g, but with the Odd Bounceimage rotation system replaced with a second Polarizer.

FIGS. 1 l-1 o demonstrate various element configurations for a Terahertzellipsometer or polarimeter.

FIG. 1 p shows specific Terahertz ellipsometer or polarimeter.

FIGS. 2 a-2 d show various aspects of Terahertz frequency Sources.

FIGS. 2 e-2 g show demonstrative detectors of Terahertz frequencies.

FIG. 3 a demonstrates an Odd Bounce image rotating system comprisingthree (3) reflecting elements.

FIG. 3 b demonstrates an Odd Bounce image rotating system comprisingfive (5) reflecting elements.

FIG. 4 demonstrates a preferred compensator (C) (C′) C″) which has beenused in a rotating compensator ellipsometer system for application inthe IR range of wavelengths.

FIG. 5 a demonstrates a combined Non-Brewster Angle and Brewster AnglePolarizer system.

FIG. 5 b demonstrates a dual tipped wire grid polarizer system.

FIG. 6 demonstrates data which can be achieved by application of thePresent Invention, including in an overlap frequency range between about1.0 and 1.4 THz.

FIG. 7 demonstrates displaying data obtained by practice of the presentinvention using a computer.

FIG. 8 a shows a preferred embodiment of a present invention THZellipsometer or polarimeter.

FIG. 8 a′ shows a more detailed preferred embodiment of a presentinvention THZ ellipsometer or polarimeter.

FIG. 8 b shows that the FIG. 8 a preferred embodiment of a presentinvention THZ ellipsometer or polarimeter can be rotated to enableachieving different angles-of-incidence (AOI).

FIG. 9 shows a system for enabling the present invention FIGS. 8 a and 8b embodiments to be applied to investigating samples on a horizontallyoriented stage.

FIG. 10 a shows an embodiment of the FIGS. 8 a and 8 b rotating retarder(RRET).

FIG. 10 b shows a preferred embodiment of the FIGS. 8 a and 8 b rotatingretarder (RRET).

FIGS. 10 c-10 e show additional embodiments of the FIGS. 8 a and 8 brotating retarder (RRET).

DETAILED DESCRIPTION

At the outset attention is directed to FIG. 8 a, which shows a preferredpresent invention Terahertz Ellipsometer sequentially system comprising:

-   -   a source (BWO) of terahertz electromagnetic radiation;    -   a first rotatable polarizer (WGP1);    -   a stage (STG) for supporting a sample (S);    -   a second rotatable polarizer (WGP2);    -   a detector (DET) of terahertz electromagnetic radiation.        Said terahertz ellipsometer or polarimeter system further        comprises a first rotating element (RE1) and second rotating        element (RE2) between said source and detector of        electromagnetic radiation.        In use said source of terahertz electromagnetic radiation        directs a beam (BI) of terahertz frequency electromagnetic        radiation of a fundamental frequency to pass through said first        rotatable polarizer, then reflect from a sample (S) placed on        said stage (STG) for supporting a sample, then pass-through said        second rotatable polarizer, and as output beam (BO) enter said        detector of electromagnetic radiation as output beam (BO),        wherein said beam also passes through said first rotating        element (RE1) and second rotating element (RE2).

FIG. 8 a′ shows a more detailed preferred presently disclosed terahertzellipsometer sequentially system comprising:

-   -   a backward wave oscilator (BWO);    -   an optional frequency multiplier (FM);    -   an optional first concave parabolic mirror (PM1);    -   an optional reflecting means (M1);    -   a first rotatable wire grid polarizer (WGP1);    -   an optional second concave parabolic mirror (PM2);    -   a rotating wire grid polarizer (RWGP);    -   a stage for (STG) supporting a sample (S);    -   a rotating retarder (RRET) (comprising first, second, third and        fourth elements as shown in FIGS. 10 a-10 e); said FIG. 10 b        demonstrating a preferred arrangement of:        -   first (RP), second (RM1), third (RM2) and fourth (RM3)            reflective elements from each of which, in use, an            electromagnetic beam reflects once,        -   said first reflective element (RP) being prism (RP) which            receives a beam through a first side thereof and exits a            reflected beam through a third side thereof,    -   said reflection being from a second side thereof oriented at        prism forming angles to said first and third sides;    -   said elements (RP) (RM1) (RM2) (RM3) being oriented with respect        to one another such that the locus of the beam reflecting from        the second side of said prism approaches said second reflective        side thereof at an angle equal to or greater than that required        to achieve total internal reflection within said prism (RP),    -   and such that the locus of beam reflected from the fourth        element in the sequence of elements is substantially colinear        and without deviation or displacement from the locus of the beam        received by the first element in said sequence of elements,    -   an optional third concave parabolic mirror (PM3);    -   a second rotatable wire grid polarizer (WGP2);    -   an optional fourth concave parabolic mirror (RM1); and    -   a golay cell detector (DET).

Assuming optional elements are present, in use said backward waveoscillator (BWO) directs a beam of terahertz frequency electromagneticradiation of a fundamental frequency to said frequency multiplier (FM),from which frequency multiplier (FM) a beam comprising a desiredfrequency is caused to be reflected from said first concave parabolicmirror (PM1) as a substantially collimated beam, said substantiallycollimated beam then being directed to reflect from said reflectingmeans (M1) and pass through said first rotatable wire grid polarizer(WGP1) and reflect from said second concave parabolic mirror (PM2)through said rotating wire grid polarizer (RWGP), then reflect from asample (S) placed on said stage (STG) for supporting a sample, then passthrough said rotating retarder (RRET), reflect from said third parabolicmirror (PM3), pass through said second rotatable wire grid polarizer(WGP2), then reflect from said fourth concave parabolic mirror (PM4) andenter said golay cell detector (DET).

FIG. 8 b shows that that the FIGS. 8 a and 8 a′ terahertz ellipsometersystem can further comprise means for rotating, as a unit, said:

-   -   stage (STG) for supporting a sample (S);    -   rotating retarder comprising first (RP), second (RM1), third        (RM2) and fourth (RM3) elements,    -   third concave parabolic mirror (PM3);    -   second rotatable wire grid polarizer (WGP2);    -   fourth concave parabolic mirror (PM4); and    -   golay cell detector (DET);        about a vertical axis centered at a midpoint of said stage (STG)        for supporting a sample (S) such that the angle of incidence (θ)        at which said beam of terahertz frequency electromagnetic        radiation approaching from said rotating wire grid polarizer        (RWGP), and the angle of reflection (θ) of said beam from said        sample (S) placed on said stage (STG) for supporting a sample,        can be adjusted.

FIG. 8 b is to also be interpreted to, in addition, or as an option,enable said terahertz′ellipsometer system to further comprise means forrotating, as a unit, said:

-   -   backward wave oscilator (BWO);    -   frequency multiplier (FM) if present;    -   first concave parabolic mirror (PM1) if present;    -   reflecting means (M1) if present;    -   rotatable wire grid polarizer (WGP1);    -   second concave parabolic mirror (PM) if present;    -   rotating wire grid polarizer (RWGP);        about a vertical axis centered at a midpoint of said stage (STG)        for supporting a sample (S) such that the angle of incidence (θ)        at which said beam of terahertz frequency electromagnetic        radiation approaching from said rotating wire grid polarizer        (RWGP), and the angle of reflection (θ) of said beam from said        sample (S) placed on said stage (STG) for supporting a sample,        can be adjusted.

In practice either the components on the Source (BWO) and/or Detector(DET) side of the Stage (STG), along with the stage can be rotated toset an Angle-of-Incidence of a Terahertz beam onto a sample.

The terahertz ellipsometer system can further comprise a beam chopper(CHP), said beam chopper (CHP) being of any functional design, buttypically being a rotating wheel with a plurality of openings thereinthrough which the terahertz electromagnetic radiation beam can pass,said chopper being placed the locus of the terahertz electromagneticradiation beam at some point between said backward wave oscilator andsaid golay cell detector, said wheel being made from high densitypolyethelyene. Note the position of the chopper (CH) in FIG. 8 a′ isdemonstrative, not limiting. The chopper (CHP) can be located at anyfunctional location in the terahertz ellipsometer system.

It is noted that said terahertz ellipsometer system is typicallyoriented to mount samples (S) to said stage (STG) for supporting asample so that said sample (S) is in a vertical plane as observed inlaboratory coordinates. FIG. 9 shows a system that allows said terahertzellipsometer system to orient the stage (STG) for supporting a sample(S) in a horizontal plane. Note that the stage (STG) for supporting asample (S) is oriented to support a sample in a horizontal plane and inwhich the beam is directed thereto via left and right verticalsequences, each of first (FLS/FRS) second (SLS/SRS) and third (TLS/TRS)elements, such that the terahertz frequency electromagnetic beam exitingsaid rotating wire grid polarizer (RWGP) reflects from the first leftside element (FLS) to the second left side element (BLS), then to thethird right side element (TRS), from which it is directed to reflectfrom a sample (S) placed on the stage (STG) in a horizontal plane towardthe third left side element (TLS), which reflects said beam to thesecond right side element (SRS) toward said first right side element(FRS), from which said beam is directed into said rotating retarder(RRET), (see FIG. 8 a).

It is noted that in use terahertz ellipsometer system rotating wire gridpolarizer (RWGP) and the rotating retarder (RRET) comprising first (RP),second (RM1), third (RM2) and fourth (RM3) elements are preferably, butnot necessarily, rotated at relative speeds with respect to one anotherthat form a ratio in the range of 1 to 10 or 10 to 1.

FIG. 10 a shows that the terahertz ellipsometer system rotating retarder(RDT) can comprise a prism (RP), which receives a beam orientedperpendicular to a first side thereof and exits a reflected beamoriented perpendicular to a second side thereof, said reflection being atotal internal reflection from a side oriented at forty-five degreeangles to said first and second sides, is positioned to be the firstelement the terahertz frequency electromagnetic beam encounters. Alsoshown present are reflecting elements (RM1) (RM2) and (RM3) to provide afour element rotating retarder, which it is mentioned, is functionallyequivalent to a ½ wave plate. It is also noted that, while notpreferred, the positions of (RP), and any one of the (RM1) (RM2) (RM3)can be swapped and a retarder (RET) which can be applied in use stillresults.

FIG. 10 b shows a preferred rotating retarder (RRET) comprising, in anyfunctional order, first (RP), second (RM1), third (RM2) and fourth (RM3)reflective elements from each of which, in use, an electromagnetic beamreflects once, said first reflective element (RP) being prism (RP) whichreceives a beam through a first side thereof and exits a reflected beamthrough a third side thereof, said reflection being from a second sidethereof oriented at prism forming angles to said first and third sides;said elements (RP) (RM1) (RM2) (RM3) being oriented with respect to oneanother such that the locus of the beam reflecting from the second sideof said prism approaches said second reflective side thereof at an angleequal to or greater than that required to achieve total internalreflection within said prism (RP), and such that the locus of beamreflected from the fourth element in the sequence of elements issubstantially colinear and without deviation or displacement from thelocus of the beam received by the first element in said sequence ofelements.

FIGS. 10 c-10 e indicate that while the FIG. 10 a embodiment ispreferred, any functional order of the first (RP), second (RM1), third(RM2) and fourth (RM3) reflective elements can be applied in anyfunctional order. Again, said first reflective element (RP) is a prismin which total internal reflection occurs.

Previously Disclosed Support

Turning now to previously disclosed Drawings that are included forsupport of the present preferred embodiment of the invention shown inFIGS. 8 a-10 d, FIGS. 1 a, 1 b and 1 c show various approaches toproviding a THZ Ellipsometer System. FIG. 1 a shows Three Sources (S1)(S2) S3), which can each be a backward wave oscillator or aSmith-Purcell cell or a free electron laser or a solid state device.Also demonstrated are Beam Combiners (BC1) (BC2) (BC3) which serve todirect electromagnetic radiation from Sources (S1) (S2) S3),respectively, toward a Sample (S), via optional Polarizer (P), (thenatural source polarization can suffice), Odd Bounce Image RotatingSystem (OB) and Compensator (C). Said optional (P) (OB) (C) componentsare shown as typically, in combination, being termed a ConventionalPolarization State Generator (CPSG) and are included to polarize a beamof electromagnetic radiation provided by a Source (S1) (S2) S3). It ispossible, however, that a selected Source (S1) (S2) S3) can provide abeam of electromagnetic radiation which is already polarized, therefore,in this Specification it is to be understood that it is within thedefinition of “Polarization State Generator (PSG)” that it comprise theSource (S1) (S2) S3) with or without the presence of ConventionalPolarization State Generator (CPSG) components. FIG. 1 a also shows thatoptional (OB′) (C′) and (P) components between the Sample (S) and aDetector (D1) D2). Note that Detectors (D1) and (D2) haveelectromagnetic radiation directed thereinto by BeamSplitters/Directors. In use Source (S1) (S2) and (S3) can be energizedor not so that a beam of electromagnetic radiation progressing towardthe Sample (S) comprises various ranges of wavelengths. For instance,Source (S1) can be selected to provide Terahertz (Thz) frequencies, andSource (S2) selected to provide Infrared (IR) frequencies, and duringuse one or the other can be energized so that only (THz) or (IR)wavelengths are provided, or both can be energized to provide a broadcombined range of wavelengths, preferable with an overlap range ofbetween about 1.0 Thz, and 1.4 Thz or higher, frequency. The samegeneral description of FIG. 1 a applies to FIGS. 1 b and 1 c, with theexception that the Sources and Detectors are shown as configureddifferently. In FIG. 1 b the Sources (S1) (S2) (S3) and Detectors (D1)(D2) (D3) are simply sequentially slid into position. In FIG. 1 c, InputBeam Reflecting Means (BRI) and Output Beam Reflecting Means (BRO) areshown as being rotatable to selectively direct electromagnetic radiationfrom one source or another toward the Sample (S). The configurationsshown in FIGS. 1 a-1 c are not to be considered. limiting, but ratherare demonstrative. For instance, it is possible to choose a FIG. 1 aSource selection approach, and a FIG. 1 b or 1 c Detector selectionarrangement etc. And it is possible to provide only one Source, (ie. aTerahertz frequency providing system), while providing a selectionbetween two Detectors (eg. a Golay cell or Bolometer).

It is also noted that the configuration in FIG. 1 a can be operated witha plurality of Sources simultaneously turned on to provide anelectromagnetic beam which contains a broad frequency range. Especially,but not exclusively, in such a configuration it is beneficial to adjustsaid sources providing output in the range of 1.0 to 1.4 THz such thatsubstantially the same results, (eg. ellipsometric PSI and/or DELTA),are achieved by analyzing output from any of the selected detectors inthe frequency range of between about 1.0 to 1.4 THz. This not onlyprovides continuity between the lower and upper extents of the frequencyrange, but provides an approach to assuring accuracy of results. If thesame results are achieved using very different sources ofelectromagnetic radiation, both can be considered to very likelyenabling acquisition of good data.

FIG. 1 d is included to disclose that an Alternative. Polarization StateGenerator (APSG) configuration involving an optional Polarizer (P) and aModulator (MOD), can be applied. Such an (APSG) configuration can beemployed instead of, or in addition to components in the ConventionalPolarization State. Generator (CPSG) shown in FIGS. 1 a-1 c. Alsoindicated is an Alternative Polarization State Detector Generator (APSD)configuration including a Modulator (MOD′). Again such an (APSD)configuration can be employed instead of, or in addition to theConventional Polarization State Detector (CPSD) shown in FIGS. 1 a-1 c.It is noted that various types of Modulators exist, including thosewhich apply an electric signal, or an acoustic signal or an opticalsignal to effect modulation of a polarization state.

Also shown in FIGS. 1 a-1 d is a Chopper (CH). This allows the beam tobe “chopped” at a selected frequency so that it can be monitoredseparate from non-chopped background electromagnetic radiation. Thisenables obtaining data which is not overwhelmed by noise, in anon-darkened room. The Chopper (CH) is shown a being located differentlyin each of FIGS. 1 a-1 d. This is to indicate that there is no requiredposition, with the only functional requirement being that the beam bechopped thereby. The system which comprises a Chopper (CH) will providesubstantially only the chopped electromagnetic beam to the Detector.(D1) (D2) D3).

FIG. 1 e shows a system substantially similar to that in FIG. 1 a, butnote that the Odd Bounce Image Rotating System (OB) precedes thePolarizer (P) in the Polarization State Generator (PSG). FIG. 1 h alsoindicates that both the Odd Bounce Image Rotating System (OB) andPolarizer (P) are fitted with means, (eg. stepper motors), for effectingsynchronized rotation of (MOB) and (MOP). In use a natural polarizationstate from the Source (S1) is azimuthally rotated by the Odd BounceImage Rotating System (OB) and then passes through the Polarizer (P). Inthis system the Polarizer (P) is rotated azimuthally to correspond tothe azimuthal position of the polarization in the electromagnetic beamas it exits the Odd Bounce Image Rotating System (OB). This approach hasbeen found to work very well. The Odd Bounce Image Rotating System (OB)is substantially responsible for setting the azimuthal orientation ofthe beam polarization, and the Polarizer (P) “cleans-up” polarization ofthe beam exiting therefrom. FIGS. 1 f and 1 g are again very similar toFIGS. 1 b and 1 c, but with a similar reversal of position of the OddBounce Image Rotating System (OB) and the Polarizer, for the samepurpose as indicated with respect to FIGS. 1 e and 1 a.

FIGS. 1 i-1 k show similar configurations to FIGS. 1 e-1 g, but notethat a second Polarizer (P′) replaces the Odd Bounce Image RotatingSystems (OB) in FIGS. 1 e-1 g. In this case the second Polarizer (P′)serves to prevent Polarizer (P) being oriented so that it is at 90degrees with respect to the natural polarization emerging from theSource (1) (S2) (S3), therefore blocking its transmission therethrough.By adding Polarizer (P′) it is possible to set Polarizer (P) at anyazimuthal orientation and still achieve electromagnetic beamtransmission there through.

FIGS. 1 l-1 o demonstrate various element configurations for a Terahertzellipsometer or polarimeter.

FIGS. 1 l and 1 p show a Backward Wave Oscillator (BWO) is shown asSource for providing a partially linearly polarized Beam ofelectromagnetic radiation which is directed to pass through a focusingLens (L), a Chopper (C), an Image Rotator (PR), a Polarizer (P) theninteract with a Sample on a Stage (S), and then pass through a RotatingAnalyzer (A) and enter a Golay Cell Detector (GC). More specificallyFIG. 11 p demonstrates an ellipsometer or polarimeter systemsequentially comprising:

-   -   a backward wave oscillator (BWO);    -   optionally a focusing lens (L);    -   a rotatable image rotation system (PR);    -   a rotatable wire grid polarizer (P);    -   a sample supporting stage (S);    -   a rotating analyzer (A);    -   a Golay cell (GC);        said ellipsometer or polarimeter system further comprising:    -   an optical chopper (CH);        between said backward wave oscillator (BWO) and said Golay cell        (GC);        such that in use a polarized beam of Terahertz spectral range        electromagnetic radiation is provided by said backward wave        oscillator (BWO), is optionally focused by the focusing lens        (L), has its polarization state rotated by said rotatable image        rotation system (PR) and passes through said rotatable wire grid        polarizer (P), then impinges on a sample placed on said sample        supporting stage (S), reflects therefrom and passes through said        analyzer and enters said Golay cell;        said ellipsometer or polarimeter system being distinguished in        that, during data acquisition, the rotatable image rotation        system (PR) and rotatable wire grid polarizer (P) are        functionally stepwise rotated in tandum, wherein said rotatable        wire grid polarizer (P) is stepwise rotated through a sequence        of angles twice that of the rotatable image rotation system        (PR), such that the polarization state of the beam provided to        the wire grid polarizer (P) by the rotatable image rotation        system PR), is passed by said rotatable wire grid polarizer (P)        even where the polarization state of the polarized beam of        Terahertz spectral range electromagnetic radiation from the        backward wave oscillator (BWO) is rotated by 90 degrees.

Said ellipsometer or polarimeter system can provide that said rotatableimage rotation system (PR) is an odd bounce (OB) (OB′) optical imagerotating system comprising an odd number of at least three (RE1) (RE2)(RW3) reflective elements, (see FIGS. 3 a and 3 b), oriented such that abeam of electromagnetic radiation provided by said source ofelectromagnetic radiation (BWO) interacts with each of said at leastthree reflective (RE1) (RE2) (RW3) elements of said at least one oddbounce optical image rotating system (PR) and exits therefrom along anon-deviated non-displaced trajectory, said beam of electromagneticradiation also interacting with a sample system placed on said stage forsupporting a sample system (S), and said analyzer (A) before enteringsaid detector (GC). It is noted that the at least one odd bounce (OB)(OB′) optical image rotating system consists of a selection from thegroup consisting of:

-   -   three (RE1) (RE2) (RW3); and    -   five (RE1′) (RE2′) (RW3′) (RE4′) (RE5′);        reflective elements.

FIG. 1 p shows that said ellipsometer or polarimeter system which canfurther comprises at least one beam directing reflecting means (M1) (M2)(M3) (M4). Further, the sample supporting stage (S) can be part of asystem (HG) for controlling the angle of incidence (0a) at which a beamof electromagnetic radiation is caused to approach said sample.

Reference to FIGS. 1 a-1 o should be understood to show that the FIG. 1p system can comprise at least one rotatable or rotating polarizer,compensator and/or analyzer.

FIG. 1 m is not to be confused with that in FIGS. 1 l and 1 p. Shows avariation of the Rotating Analyzer THZ Ellipsometer system wherein theImage Rotating System is replaced with a second Polarizer (P2). In userelative rotation of Polarizers (P1) and (P2) adjusts the amount ofpolarized beam which exits (P2).

FIG. 1 n shows a Rotating Polarizer THZ Ellipsometer system. Note thatcompared to FIG. 1 l, FIG. 1 n shows a Rotating Polarizer (RP) and acombination of Rotatable Analyzer (A) and Image Rotator (PR) after theSample and Stage (S). The order of the Rotatable Analyzer (A) and ImageRotator (PR) can be reversed.

FIG. 1 o shows a Rotating Compensator THZ Ellipsometer system. Note thatboth the Polarizer (P) and Analyzer (A) are rotatable, and an additionalRotating Compensator (RC) element, is present.

Turning now to FIGS. 2 a-2 d, insight to the operation of variousTerahertz sources is provided. FIG. 2 a shows that a Smith-Purcell (SP)cell comprises a Grating (G) and an electron beam (e⁻) passingthereover, with the result being that THz electromagnetic radiation isemitted. FIG. 2 b shows that a Free Electron Laser (FE) comprises asequence of Magnetic Poles (MP), and again an electron beam (e⁻) passingthereover, with the result being that THz electromagnetic radiation isemitted. FIG. 2 c shows a Backward Wave Oscillator (BWO) comprises aWaveguide (WG) through which electromagnetic radiation (EM) is passed inone direction while an electron beam (e⁻) passes therethrough in theopposite direction, again with the result that THz electromagneticradiation is emitted. FIG. 2 d demonstrates that a Terahertz source,(arbitrarily identified as (S1)), typically requires that a FrequencyMultiplier (M) be present to provide an extended frequency range output,(eg. from 300 GHz or below through at least 1.4 THz). While notdiagramatically shown, as there is really nothing to show, it is notedthat an IR range Source of electromagnetic radiation is preferably aFourier Transform Infrared (FTIR) Source which provides a spectroscopicrange of wavelengths. It is noted that (FTIR) actually refers to anapproach in analysis of a spectrum of wavelengths involving use of ameans for collecting a multiplicity of wavelengths simultaneously, andapplication of a Fourier Transform to data, rather than via use of amonochromator. However, it is common to identify the Source of thespectrum of IR wavelengths as an FTIR Source. It is specifically notedthat while the Odd-Bounce Image Rotation System, (see FIGS. 3 a and 3b), is present in the IR-VASE (Reg. TM), it has never been applied atfrequencies below 10 THz. And specifically, it has not been applied insystems comprising a Backward Wave Oscillator (BWO) or a Smith-Purcellcell or a Free Electron Laser which provide frequencies down to 300 GHzor below. The application thereof at said frequencies is new with thedescribed system. It is also new with the present invention to combine aFTIR Source with a Backward Wave Oscillator (BWO) or a Smith-Purcellcell or a Free Electron Laser to provide a practical system forpracticing ellipsometry over a wide frequency range of from 300 GHz orbelow upward through the IR range.

FIGS. 2 e and 2 f demonstrate basic components of Detectors, (eg. Golaycell (GC) and Bolometer (BOL)). A Golay cell basically comprises twoChambers (CH1) and (CH2). In use electromagnetic radiation (EM) entersone Chamber (CH1) and heats a gas therein, which expands. This causesthe Diaphram (DIA) to change shape which causes a Probe Beam (PB)entered to the Second Chamber (CH2) to reflect along a different pathwaywhich is then detected by a detector (not shown). FIG. 2 f shows that aBolometer (BOL) operates by directing a electromagnetic radiation toimpinge on a material (Ω) which changes resistance with its temperature.Also shown are a Voltage Source (V) and a Current Detector (I). In use achange in the current flow indicates that the electromagnetic radiationhas heated the material (Ω). FIG. 2 g show a demonstrative detector ofTerahertz frequencies comprises a P/N junction onto whichelectromagnetic radiation (EM) is impinged, and which produces ameasurable voltage (V). Further, while many materials can be applied insolid state devices, a particularly relevant material for application inTHz and IR frequency ranges is disclosed as being “Deuterated TriglycineSulfate”, which is typically referred to as (DTGS), optionally embeddedin Poly-Vinylidene Fluroide (PVDF). Said material shows very highpyroelectric performance.

(Note, FIG. 2 g should also be considered to present at least a portionof a solid state Source of Terahertz frequencies, wherein a voltage isapplied, and electromagnetic radiation emission results. It is to beunderstood that Solid State Sources and Detectors for providing anddetecting THz and/or IR frequency range electromagnetic radiation can besubstituted for, or used in combination with any of the other types ofSource and Detector types identified herein).

Turning now to FIGS. 3 a and 3 b, there is represented in FIG. 3 a athree (3) bounce Odd Bounce image rotating system (OBIRS) comprisingthree (3) reflective elements (RE1), (RE2) and (RE3), oriented withrespect to one another such that an input beam of electromagneticradiation (EMI) exits as an output beam of electromagnetic radiation(EMO) without any deviation or displacement being entered into the locusthereof. FIG. 3 b demonstrates a five (5) bounce odd bounce imagerotating system (OBIRS) wherein five reflective elements (RE1′), (RE2′)(RE3′), (RE4′) and (RE5′) oriented with respect to one another such aninput beam of electromagnetic radiation (EMI) exits as an output beam ofelectromagnetic radiation (EMO) without any deviation or displacementbeing entered into the locus thereof. Note generally that the angle ofincidence of the (EMI) and (EMO) beams of electromagnetic radiation arenearer normal than is the case in the FIG. 3 a three (3) bounce oddbounce image rotating system (OBIRS). This is beneficial in that thecloser to normal the angle of incidence, the less aberration effects areentered to the beam. However, it is also to be appreciated thatconstruction of the FIG. 3 b system is more difficult than isconstruction of a FIG. 3 a system.

FIG. 4 demonstrates a preferred compensator (C) (C′) for use in arotating compensator ellipsometer system for application in the IR rangeof wavelengths. The compensator system comprises, as shown in uprightside elevation, first (OS1) and second (OS2) orientation adjustablemirrored elements which each have reflective surfaces. Note theadjustability enabling pivot (PP1) (PP2) mountings. Said compensatorsystem further comprises a third element (TE) which, as viewed inupright side elevation presents with first (IS1) and second (IS2) sideswhich project to the left and right and downward from an upper point(UP2), said third element (TE) being made of material which providesreflective interfaces on first and second sides inside thereof. Saidthird element (TE) is oriented with respect to the first (OS1) andsecond (OS2) orientation adjustable elements such that in use an inputelectromagnetic beam of radiation (LB) caused to approach one of saidfirst (OS1) and second (OS2) orientation adjustable mirrored elementsalong an essentially horizontally oriented locus, is caused toexternally reflect therefrom upwardly vertically oriented, (see beam(R1)) then enter said third element (TE) and essentially totallyinternally reflect from one of said first and second sides thereof, thenproceed along an essentially horizontal locus (see beam (R2)), andessentially totally internally reflect from the other of said first(OS1) and second (OS2) sides and proceed along an essentially downwardvertically oriented locus, (see beam (R3)), then reflect from the otherof said first (OS1) and second (OS2) adjustable mirrored elements andproceed along an essentially horizontally oriented (LB′) propagationdirection locus which is essentially undeviated and undisplaced from theessentially horizontally oriented locus of said input beam ofelectromagnetic radiation even when said compensator is caused to rotateabout the locus of the beam of electromagnetic radiation, with theresult being that retardation is entered between orthogonal componentsof said input electromagnetic beam of radiation. Also shown are thirdelement lower side (IS3), with indication that it can be shaped as shownby (IS3′), and retain functionality.

FIGS. 5 a and 5 b demonstrate systems which can be used as Polarizer (P)and Analyzer (A) in FIGS. 1 a-1 c. FIG. 5 a demonstrates a Polarizer (P)comprised of Non-Brewster Angle (NBR) and Non-Brewster (BR) Anglecomponents. Shown is a beam of electromagnetic radiation (EMW) passingdemonstrates a compensator design for optional compensators (C) (C′)will be present and caused to rotate during data acquisition and the oddbounce image rotating system (OBIRS) will be stepped to variousazimuthal angle positions and set motionless during data acquisition,which the fixed linear polarizer (FP) and analyzer (A) (A′) are heldstationary. That is, the preference is in a rotating compensatorellipsometer system, wherein the combination of the fixed polarizer andthe odd bounce image rotating system (OBIRS) provide an effectiverotatable polarizer. This is useful where a polarizer, (such as tippedwire grid plate polarizers used in the IR wavelength range), isdifficult to rotate while maintaining alignment of the componentstherein and while avoiding deviation and displacement affects betweeninput (EMI) and output (EMO) electromagnetic beams.

FIG. 5 b demonstrates an alternative possible polarizer, comprising adual tipped wire grid polarizer system comprising first (WG1) and second(WG2) wire grid polarizers which have fast axes of polarization orientedwith their fast axes parallel to one another, each thereof having firstand second essentially parallel surfaces. Note however, that theessentially parallel sides of (WG1) are tipped with respect to theessentially parallel sides of (WG2), as characterized by the angle (∝).The purpose of angle (∝) is to divert unwanted reflections (R1) and(R2).

Note that both Polarizers in FIGS. 5 a and 15 b provide substantiallyundeviated and undisplaced output beams therefrom, with respect to beamsinput thereto, even when the polarizer is rotated about the locus of abeam of electromagnetic radiation.

It is to be understood that while preferred embodiments of Polarizersprovide a linear polarization as output, the described system can beused with a substantially linearly polarizing polarizer, or a polarizerwhich provides partially linearly polarization. In the Claims the term“polarizer” should then be interpreted broadly to mean preferably alinear polarizer, but including polarizers which provide partiallylinearly polarization. Further, in combination with a Compensator, otherpolarization states can be achieved.

FIG. 6 shows that a preferred embodiment of the system allows sampleinvestigation in both the THz and IR ranges, (eg. from 300 GHz to abut1.4 THz, and from about 1.10 THz and higher frequency). Further, it isindicated that below about 1.4 THz a first (S1) is used to provide theelectromagnetic radiation, and above about 1.0 THz a second (S2) Sourceis used to provide the electromagnetic radiation. FIG. 6 shows anoverlap in the range of about 1.0 to about 1.4 THZ, and that a describedsystem preferably provides the same results, (eg. ellipsometic PSIand/or DELTA), when Detector output is analyzed to provide, forinstance, a Sample characterizing PSI (ψ), (or DELTA (Δ)). FIG. 6 shouldbe viewed as demonstrating a concrete and tangible presentation ofresults which can be achieved by application of a described Invention.

FIG. 7 demonstrates displaying data (DIS) provided by a Detector (DET),(eg. D1, D2 D3 in FIGS. 1 a-1 d), obtained by practice of describedsystems using machine readable media of a computer (CMP), as well asindicates the Computer (CMP) can control Ellipsometer/Polarimeterelements operation.

Finally, it is specifically disclosed that a present invention systempreferably comprises a Computer System which controls element motion,(eg. stepwise or continuous rotation of a Polarizer (P) and/orCompensator (C, C′) and/or Analyzer (A) and/or Odd Bounce Image RotatingSystem (OB); operation of a Chopper (CH); positioning of a Sample (S);selection of a Source (S1, S2); selection of a Detector (D1, D2, D3);and operation of a Source (S1, S2, S3) and/or Detector (D1, D2, D3).Further, a present invention system comprises a Computer System (CMP)which serves to analyze data provided by a Detector (D1, D2, D3) andDisplay said data or results of analysis thereof. That is, a presentinvention system can be considered to be a Computer System (CMP) whichcomprises an Ellipsometer or Polarimeter, which Computer System (CMP)controls operation of elements of said Ellipsometer or Polarimeter tothe end that Sample characterizing Data is developed, as well asanalysis of said data performed and presentation of said data, orresults of analysis thereof.

Having hereby disclosed the subject matter of the present invention, itshould be obvious that many modifications, substitutions, and variationsof the present invention are possible in view of the teachings. It istherefore to be understood that the invention may be practiced otherthan as specifically described, and should be limited in its breadth andscope only by the Claims.

I claim:
 1. A method of determining physical and optical properties ofsamples using a terahertz frequency electromagnetic radiation,comprising the steps of: a) providing a terahertz ellipsometer orpolarimeter system sequentially system comprising: a backward waveoscillator (BWO); a rotatable polarizer comprising a wire grid (WGP1); arotating polarizer comprising a wire grid (RWGP); a stage (STG) forsupporting a sample (S); a rotating retarder (RRET) comprising, in anyfunctional order, first (RP), second (RM1), third (RM2) and fourth (RM3)reflective elements from each of which, in use, an electromagnetic beamreflects once, said first reflective element (RP) being prism (RP) whichreceives a beam through a first side thereof and exits a reflected beamthrough a third side thereof, said reflection being from a second sidethereof oriented at prism forming angles to said first and third sides;said elements (RP) (RM1) (RM2) (RM3) being oriented with respect to oneanother such that the locus of the beam reflecting from the second sideof said prism approaches said second reflective side thereof at an angleequal to or greater than that required to achieve total internalreflection within said prism (RP), and such that the locus of beamreflected from the fourth element in the sequence of elements issubstantially colinear and without deviation or displacement from thelocus of the beam received by the first element in said sequence ofelements; a second rotatable polarizer comprising a wire grid (WGP2); aGolay cell detector (DET); such that in use said backward waveoscillator (BWO) directs a beam (BI) of terahertz frequencyelectromagnetic radiation of a fundamental frequency to pass throughsaid first rotatable polarizer comprising a wire grid (WGP1), thenthrough said rotating polarizer comprising a wire grid (RWGP), thenreflect from a sample (S) placed on said stage (STG) for supporting asample, then pass through said rotating retarder (RRET), then passthrough said second rotatable wire grid polarizer (WGP2), enter saidGolay cell detector (DET) as output beam (BO); b) placing a sample (S)on said stage (STG) for supporting samples; c) causing said backwardwave oscillator (BWO) to direct a beam (BI) of terahertz frequencyelectromagnetic radiation Of a fundamental frequency to pass throughsaid first rotatable wire grid polarizer (WGP1) and then through saidrotating polarizer comprising a wire grid (RWGP), then reflect from asample (S) placed on said stage (STG) for supporting a sample, then passthrough said rotating retarder (RRET), then pass through said secondrotatable polarizer comprising a wire grid (WGP2), and enter said Golaycell detector (DET) as output beam (BO); d) obtaining sample describingdata from said Golay cell detector (DET).
 2. A method as in claim 1, inwhich the step of providing a terahertz ellipsometer or polarimetersystem further comprises providing: a frequency multiplier (FM)following said backward wave oscillator (BWO); a first concave parabolicmirror (PM1); and a reflecting means (M1); prior to said rotatablepolarizer comprising a wire grid (WGP1); and which further sequentiallycomprises after said rotatable polarizer comprising a wire grid (WGP1);a second concave parabolic mirror (PM2); prior to said a rotatingpolarizer comprising a wire grid (RWGP); there also further sequentiallybeing, after said rotating retarder (RRET), a third concave parabolicmirror (PM3); and there also further sequentially being, after saidsecond rotatable polarizer comprising a wire grid (WGP2); a fourthconcave parabolic mirror (PM4) prior to said Golay cell detector (DET);such that in use said backward wave oscillator (BWO) directs a beam (BI)of terahertz frequency electromagnetic radiation of a fundamentalfrequency to said frequency multiplier (FM), from which frequencymultiplier (FM) a beam comprising a desired frequency is caused to bereflected from said first concave parabolic mirror (PM1) as asubstantially collimated beam, said substantially collimated beam thenbeing directed to reflect from said reflecting means (M1) and passthrough said first rotatable polarizer comprising a wire grid (WGP1) andreflect from said second concave (PM2) parabolic mirror through saidrotating polarizer comprising a wire grid (RWGP), then reflect from asample (S) placed on said stage (STG) for supporting a sample, then passthrough said rotating retarder (RRET), reflect from said third parabolicmirror (PM3), pass through said second rotatable polarizer comprising awire grid (WGP2), then reflect from said fourth concave parabolic mirror(PM4) and enter said Golay cell detector (DET) as output beam (BO).
 3. Amethod as in claim 1 or 2 in which the sample (S) is caused to beoriented in a substantially vertical plane while data is obtained fromsaid Golay cell detector (DET).
 4. A method as in claim 1 or 2 in whichthe sample (S) is caused to be oriented in a substantially horizontalplane by application of a system comprising left and right verticalsequences of first (FLS/FRS), second (SLS/SRS) and third (TLS/TRS)elements, such that the terahertz frequency electromagnetic beam exitingsaid rotating polarizer comprising a wire grid (RWGP) reflects from thefirst left side element (FLS) to the second left side element (SLS),then to the third right side (TRS) element, from which it is directed toreflect from a sample (S) placed on the stage (STG) in a substantiallyhorizontal plane toward the third left side (TLS) element, whichreflects said beam to the second right side element (SRS) toward saidfirst right side element (FRS), from which said beam is directed intosaid rotating retarder (RRET).
 5. A method as in claim 1 or 2, whichfurther comprises providing means for rotating, as a unit at least oneselection from the group consisting of: said stage (STG) for supportinga sample (S) and said Golay cell detector (DET); and said stage (STG)for supporting a sample (S) and backward wave oscillator (BWO); about avertical axis centered at a midpoint of said stage (STG) for supportinga sample (S) such that the angle of incidence (θ) at which said beam ofterahertz frequency electromagnetic radiation approaching said sample(S) and the angle of reflection (θ) of said beam from said sample (S)placed on said stage (STG) for supporting a sample, can be adjusted; andprior to step d causing rotation of the stage (STG) about said verticalmidpoint axis of said stage.
 6. A method as in claim 1 or 2 whichfurther comprises providing a chopper (CHP), said chopper (CHP) being arotating wheel with a plurality of openings therein through which theterahertz electromagnetic radiation beam can pass, said chopper (CHP)being placed the locus of the terahertz electromagnetic radiation beamat some point between said backward wave oscillator and said Golay celldetector, and during the step d obtaining of data, causing said chopperto chop said terahertz frequency beam.
 7. A method as in claim 1 or 2 inwhich the rotating polarizer comprising a wire grid (RWGP) and therotating retarder (RRET) comprising first (RP), second (RM1), third(RM2) and fourth (RM3) elements, are rotated at relative speeds withrespect to one another that form a ratio in the range of 1 to 10 or inthe range of 10 to 1 during the step d obtaining of data.
 8. A method asin claim 1 or 2, which further comprises performing at least oneselection from the group consisting of: storing at least some dataprovided by said Golay cell detector in machine readable media;analyzing at least some of the data provided by said Golay cell detectorand storing at least some of the results of said analysis in machinereadable media; displaying at least some data provided by said Golaycell detector by a selection from the group consisting of electronic andnon-electronic means; analyzing at least some of the data provided bysaid Golay cell detector and displaying at least some of the results ofsaid analysis by a selection from the group consisting of electronic andnon-electronic means; causing at least some data provided by said Golaycell detector to produce a signal which is applied to provide a concreteand tangible result; analyzing at least some of the data provided bysaid Golay cell detector and causing at least some thereof to produce asignal which is applied to provide a concrete and tangible result.
 9. Amethod of determining physical and optical properties of samples using aterahertz frequency electromagnetic radiation, comprising the steps of:a) providing a terahertz ellipsometer or polarimeter system sequentiallysystem comprising: a backward wave oscillator source of terahertzelectromagnetic radiation; a first rotatable wire grid polarizer (RWG1);a stage for supporting a sample (STG); a second rotatable wire gridpolarizer (RWG2); a Golay cell detector (DET) of terahertzelectromagnetic radiation; said terahertz ellipsometer or polarimetersystem further comprising a first rotating element (RE1) and secondrotating element (RE2) between said source and detector ofelectromagnetic radiation; such that in use said backward waveoscillator source of terahertz electromagnetic radiation directs a beam(BI) of terahertz frequency electromagnetic radiation to pass throughsaid first rotatable wire grid polarizer (RWG1), then reflect from asample (S) placed on said stage (STG) for supporting a sample, then passthrough said second rotatable polarizer wire grid (RWG2), and as outputbeam (BO) enter said detector of electromagnetic radiation as outputbeam (BO), wherein said beam also passes through said first rotatingelement (RE1) and second rotating element (RE2); b) placing a sample (S)on said stage (STG) for supporting samples; c) causing said backwardwave oscillator (BWO) to direct a beam (BI) of terahertz frequencyelectromagnetic radiation of terahertz frequency electromagneticradiation of a fundamental frequency to pass through said firstrotatable wire grid polarizer (WGP1), then reflect from a sample (S)placed on said stage (STG) for supporting a sample, then pass throughsaid second rotatable polarizer comprising a wire grid (WGP2), and entersaid Golay cell detector (DET) as output beam (BO); said input beam (BI)of terahertz frequency electromagnetic radiation also passing throughsaid first rotating element (RE1) and through said second rotatingelement (RE2) before exiting as said output beam (BO); d) obtainingsample describing data from said Golay cell detector (DET).
 10. A methodas in claim 9, in which the step of providing a terahertz ellipsometeror polarimeter system further comprises providing: a frequencymultiplier (FM) following said backward wave oscillator (BWO); prior tosaid rotatable polarizer comprising a wire grid (WGP1); and whichfurther sequentially comprises after said rotatable polarizer comprisinga wire grid (WGP1).
 11. A method as in claim 9 or 10 in which the sample(S) is caused to be oriented in a substantially vertical plane whiledata is obtained from said Golay cell detector (DET).
 12. A method as inclaim 9 or 10 in which the sample (S) is caused to be oriented in asubstantially horizontal plane by application of a system comprisingleft and right vertical sequences of first (FLS/FRS), second (SLS/SRS)and third (TLS/TRS) elements, such that the terahertz frequencyelectromagnetic beam exiting said rotating polarizer comprising a wiregrid (RWGP) reflects from the first left side element (FLS) to thesecond left side element (SLS), then to the third right side (TRS)element, from which it is directed to reflect from a sample (S) placedon the stage (STG) in a substantially horizontal plane toward the thirdleft side (TLS) element, which reflects said beam to the second rightside element (SRS) toward said first right side element (FRS), fromwhich said beam is directed into said rotating retarder (RRET).
 13. Amethod as in claim 9 or 10, which further comprises providing means forrotating, as a unit, at least one selection from the group consistingof: Said stage (STG) for supporting a sample (S) and said Golay celldetector (DET); and said stage (STG) for supporting a sample (S) andbackward wave oscillator (BWO); about a vertical axis centered at amidpoint of said stage (STG) for supporting a sample (S) such that theangle of incidence (θ) at which said beam of terahertz frequencyelectromagnetic radiation approaching said sample (S), and the angle ofreflection (θ) of said beam from said sample (S) placed on said stage(STG) for supporting a sample, can be adjusted; and prior to step dcausing rotation of said stage (STG) said vertical midpoint axis of saidstage.
 14. A method as in claim 9 or 10 which further comprisesproviding a chopper (CHP), said chopper (CHP) being a rotating wheelwith a plurality of openings therein through which the terahertzelectromagnetic radiation beam can pass, said chopper (CHP) being placedthe locus of the terahertz electromagnetic radiation beam at some pointbetween said backward wave oscillator and said Golay cell detector, andduring the step d obtaining of data, causing said chopper to chop saidterahertz frequency beam.
 15. A method as in claim 9 or 10 in which therotating polarizer comprises a wire grid (RWGP) and the rotatingretarder (RRET) comprising first (RP), second (RM1), third (RM2) andfourth (RM3) elements, are rotated at relative speeds with respect toone another that form a ratio in the range of 1 to 10 or in the range of10 to 1 during the step d obtaining of data.
 16. A method as in claim 9or 10, which further comprises performing at least one selection fromthe group consisting of: storing at least some data provided by saidGolay cell detector in machine readable media; analyzing at least someof the data provided by said Golay cell detector and storing at leastsome of the results of said analysis in machine readable media;displaying at least some data provided by said Golay cell detector by aselection from the group consisting of electronic and non-electronicmeans; analyzing at least some of the data provided by said Golay celldetector and displaying at least some of the results of said analysis bya selection from the group consisting of electronic and non-electronicmeans; causing at least some data provided by said Golay cell detectorto produce a signal which is applied to provide a concrete and tangibleresult; analyzing at least some of the data provided by said Golay celldetector and causing at least some thereof to produce a signal which isapplied to provide a concrete and tangible result.